Living in Mexico was an adventurous fairytale; due to the variety of things to do, beauty of the country and the kindness of its residents. I am originally from Ohio but spent substantial time living in Mexico, studying the nature and history of this beautiful place. Here are some ideas and tips I learned from being there that may help you on your next trip to the Yucatan Peninsula.
Using the public bus system is infinitely cheaper than taking taxis everywhere. If you are looking for cheaper transportation to and from the airport, take the bus to downtown Playa del Carmen or Cancun. It is easy and the bus stations are centrally located in both cities. You can choose to ride an air-conditioned bus for a small amount more than the non air-conditioned bus. I would use either, who left left soonest. There are bus schedules posted for local travel or through the country. The nicest buses when I was there were the plush tour buses for longer trips, called ADO. Really nice buses that cost more but are worth it.
If you need to make phone calls in Mexico, buy a phone card there and use them from any pay phone. They can be used to call internationally as well. The locals, many of which do not have phones in their homes, use them all the time. You can buy them in the Casas de Cambio (places where you can exchange your money into Mexican pesos). A note on changing your money, check around, to look for the best exchange rates as they may vary place to place.
Those who do not scuba can enjoy the beauty of the underwater coral gardens and scenery by snorkeling. Go to the scuba shops and inquire about what excursions they offer for snorkelers, or ask your resort's front desk if you can sign up for snorkeling tours there at the hotel. Wear sunscreen while doing this daytrip, do not expect a white t-shirt to protect you, because it will not. If you do not use sun protection, you will come back lobster-red, trust me.
A word about avoiding Turista (Montezuma's Revenge, the Tourist Trots). These very unpleasant bacterial infections happen, frequently, to travelers. To avoid spending most of your vacation in the bathroom recuperating, I suggest you do not eat raw fruit (unless it's already peeled), and do not drink drinks that have ice that is not round, with a hole in it (purified water ice cubes). The large resorts' food is safe, as far as I have experienced. I've stayed in a few before moving to Mexico and never got sick by eating or drinking their food. Big resorts take precautions against contaminated foods and drink. But, out on the street, those bacteria free float into the food offered at taco stands (and I love those, by the way), and where fruit is sold. If you buy fruit, peel before eating it. If it is not peelable, then forget it. Drink purified, bottled water at all times. If you go to day-long trips out in the heat, bringing a gallon jug of water, you will need it.
Hire only qualified tour guides through reputable agencies (usually found through the hotels or your travel agent). Do not use freelance tour guides because I was told when living there that some will make information up as they go along. Independent tour guides will approach you at places like the ruins of Coba, Chichen Itza and Tulum, for example. Go with a tour group to these places. I liked the Apple tours, but there are many others that are good, too. Ask around to see who are most highly recommended. Chichen Itza is a big site, worthy of seeing, if you are going to choose a sight to see. The pyramid there, called El Castillo, is spectacular. I have been inside it (very, incredibly claustrophobic if you decide to brave it up the narrow stairway inside) and on top of it (steep stairs lead up to a few small rooms on the top, where nobility would perform rituals, etc.) Take a camera and stop at the nearby hotel for lunch if you have the chance. There was a show there where dancers in Mayan dress entertained us as our group ate there. It was a good break from the heat of sightseeing this ancient city. Word to the wise, bringing a family-size vat of sunscreen would not be a bad idea. And as much water as possible. Walking around the site all day will dehydrate and bake you if you are not careful.
Check out the cenotes (lakes of brackish water in the jungle), accessed by taking buses or taxi, along the Playa del Carmen-Tulum corridor. I liking going to the Cenote Azul or the Cenote Dos Ojos. Cenotes attract nature, and while visiting them, I saw a variety of fascinating flora and fauna from basilisk lizards to a diving duck. Cenotes are the entrance points to underwater caves, which are only safe to go to with certified dive experts. Underneath the Yucatan peninsula there are a large network of underground caves that expert divers like to explore. Do not attempt to dive these on your own, because it is dangerous. If you want to see what an underground cave is like, go near to the nature park of Xcaret, where there are underwater caves for the public to swim in.
Speaking of Xcaret, it is a must to visit if you love nature. It is full of educational activities and fun things to do for the whole family. Expect to spend an entire day there. There is swimming with dolphins, horseback riding, exploring an ancient Mayan village, seeing Mayan dancing shows, snorkeling in a large lagoon, all built into the jungles. It is a top-class place, and even has its own small zoo, butterfly garden and aviary. I know, I used to be the main illustrator for the park years ago. The restaurants are atmospheric and the food is good. Do not forget to see the Mayan musicians do their flying pole exhibition, which is done all day long. They start on top of a pole, and "fly" down, while playing their instruments, while hanging from ropes by their ankles. You will not see anything quite like it out of this region. Xcaret has a variety of natural history exhibits near their large gift shop. It is a "must" for all.
If you want a fun trip by boat, go to Playa Linda (in the Hotel Zone of Cancun) and hop a boat over to Isla Mujeres. Aqua Tours has a big, luxurious yacht that goes over there a few times a day. On the way to the island, you are served drinks, are entertained by the staff and get a great view of the Cancun coastline. Once at Isla Mujeres, you are taken on excursions to places like Tortugranja (a sea turtle farm, where they raise endangered sea turtles from small to large), or Hacienda Mundaca (a supposedly former estate of an ex-pirate, who built it for his love interest, according to local legend). They offer snorkeling, too. It's a fun day trip, and the shopping is pretty good on the island, too.
Another interesting place to visit is Merida, the capital city of the state of Quintana Roo (where Cancun is located). It reminded me of Europe, with its lovely, large mansions, outdoor cafés and sturdy buildings. There, you will find the United States embassy, among others. If you need to replace a lost passport or talk to embassy officials, this is where you want to go. It is a very international place, worth the very long bus ride from Cancun.
Downtown Cancun has a few interesting places to shop. There are authentic food and crafts at Plaza 2000, or see Chedraui (a department / grocery store), or Pelicano (another general merchandise store). I have not been to Cancun since the devastating hurricane there, so check to see if these places are still in operation, if so, they are definitely worth going to. Take a bus or taxi to these places, to get a more "authentic" Mexican experience. Staying just in the Hotel Zone is fun, but not a slice of everyday Mexican life. Try some of the great food stands where the locals go. I love the chicken cooked on spits everywhere, called "Pollo Rojo" (red chicken) due to the spices used. It is to die for and incredibly cheap. If you see people on the street selling tamales, try them, they are excellent and really cheap. I could easily eat my way through Mexico by living on tamales (meat inside a corn-based "cake") and empanadas (meat turnovers) alone. If you buy bakery items in Mexico at the grocery stores, bear in mind that they use much less sugar than Americans are used to having, in their recipes. I like the Conchitas, shaped shaped shells. If you want sweets, buy the cakes sold under the brand name
"Bimbo" (yes, that is the name of it). It is a major bread and snack food producer in Mexico.
Enjoy your stay in the lovely Mayan Riviera. Walk the beaches and admire that stunningly turquoise water, it is truly paradise. Enjoy the hospitality of the friendly and helpful Mexican nationals. Remember to have fun, but remember, it is a foreign country, so obey their laws and be respectful of the differences in culture. If you go, you'll want to go back again and again. I know I did. The more you go, the more you know. Living in the Yucatan was an unforgettable experience, visiting there is too, so make it a memorable trip for yourself by seeing as much of it as you can. You will not be disappointed.