I just got back from there.. I was all inclusive, so I had a ride at the airport waiting for me to take me to the hotel!! All the food and alcohol you can drink. Believe me, I got my fair share..
Things my girl and I did..
1) Swam with the dolphins..(check around because there are some chinsy ones, and not actual swims)
2) Snorkled the coral reef.. We took a 45 min. jet ski ride out to the the reef, and snorkled for about 1 hour.. ONly other reef in the world is Australia, so its something you shouldnt miss.
3) Water Park.. Its right by the airport! It was ok, had some big water slides, and wave pool. This is where we swam with the dolphins..(highly recommend)
4) Use the buses whenever possible. Cheapest! Cab rides are min. $9US, and longer rides are $18USD.
5) Clubs are min. $40USD/each.. We got this party hopper pass for 2 for $90. It was good for 4 different clubs.. Coco Bongo is the best club there.. Daddy Os is good too.! The party hopper goes to these 2 clubs and 2 others.. The first two are ok.. All you can drink too!!
The mexicans are not afraid to ask for tips, so dont be surprised. They all try to undercut each other too, offering you the best deals.. Just be careful who you deal with.. Sometimes they are cheaper, sometimes they are more expensive.. You just have to check around and ask.. The hotel will tell you not to use anyone outside the hotel, but thats where we got the party hopper $20 cheaper!
Only was there 5 days, so we didnt get to do everything.. They have para sailing too, but we ran out of time and money!!