Most Hotels and resorts in Cancun are in the main hotel district. Very few of these hotels are inexpensive, especially the ones on the beach. We've stayed at a few of these resort hotels but were often disappointed in the beaches. Very narrow in most cases. Most of the beautiful white sand has been blown off due to recent hurricanes so often you are laying on ironstone which is very sharp and uncomfortable. Make sure you get a chair from the hotel grounds or bring your own. The water is wonderful so it makes up for the discomfort on the beaches. Unless you want a lot of glitz I recommend trying the hotels that are on the lagoon side of the island. Many have pools and they are much less expensive but still close enough to walk to the discos, eateries, and shopping malls. Try the Blue Lagoon Hotel just outside downtown. Any cabbie can take you there.
I really like this island twelve miles off the coast of northern Yucatan, it offers exquisite diving,some of the best I've ever seen with wonderful outcroppings and swim- throughs, as well as beautiful sponge and sea fans. These are all drift dives here but the current is less than 2 miles an hour. Anyone with just an open water certification can do most of these dive spots. Also there is a company called Aquasports that will take you to do some really excellent snorkeling if you are not yet a certified diver. I have seen an amazing amount of colorful fish unlike anywhere else I've dived. The accommodation's are very good and you can find decent rooms for as little as $25.00 a night. If you like all inclusive (including shore tanks) check out the Scuba Club. The Barracuda has a dive shop onsite as well. The dive boats will come pick you up right off the dock at your hotel.
"Playa del Carmen"
This is my most favorite destination in Yucatan. Once a small fishing village when I first visited in 1996, it has grown into a fairly large town with eateries and great shopping. The beaches are much wider and appealing then Cozumel or Cancun. Great food and drink on the beach with a great view of Cozumel in the distance. Walk down 5th Avenue and you will find anything you want. My favorite store is Casa de Partagas where you can get some authentic Cuban cigars. Run by a European couple who have been in business for years there, they have almost all major brands and are fairly inexpensive compared to some of the upscale shops in the resort areas. There is also a great dive shop there named Tank-Ha. Go see them if you want to dive. Need a hotel? Try La Rana Cansada. Owned by Thed and Pia. There is a bar onsite!