Several years ago I stayed at the Dreams all inclusive resort in Puerto Aventuras. The resort is small but has some nice snorkeling off the beach. Dreams had just bought the resort and the resort had some issues with the turnover. There is a great dive operation on site. If you go to my web site
http://mysite.verizon.net/vzey9dt2/hcbernwebsite/ you can see a video of me and my son diving. There is a very small town walking distance from the resort that has a dolphin research center and a show. While the resort includes food, we found a couple of restaurants in the town that had great food at great prices. There is another dive operation and dive store in the town. Also a shop where you can print out your boarding passes cheaper than the hotel charges. The hotel has transportation to Playa Carmen where you can take the ferry to Cozumel. The dive shop has a sister operation on Cozumel.
The hotel next to Dreams looked a little nicer and used the Dreams dive operator. I can't remember the name and don't know if it is all inclusive. I liked the location as it was a short ride to the Cozumel Ferry and the Talum ruins. If you want to talk on the phone, send me an email at hcbern@verizon.net and we can arrange a time.