I sent you a PM. I live there part time. In the states now but will be there when you are there. Hurricane Ivan took alot of sand from the beaches in September exposing many rocks. No more boogie boarding for a while. A must do Club is Coco Bongo. Dady O's is fun as well as The City if they have a good DJ. Nectar is the premiere afterhours club from 3am until 6 or 8am. More locals there so if you don't speak Spanish, you may not have much conversation.
Ruth Chris's Steak House opened up a few weeks ago as well as the huge new Aqua by Fiesta Americana.
Plaza La Isla is a good plaza to shop in and see movie and is in the hotel zone. If you go in town, go to Plaza Las Americas.
Fat Tuesday's is fun Tuesday nights for Mardi Gras but seeing boobs gets old after the first time there. spring Break is a blast there but other time you'd wish the girls kept their shirts on. I was almost at the point to give beads so they wouldn't flash!
For cheap drinks and fun with the locals, take the bus to the "centro" to Ave. Yaxchilan. Los Arcos has 2 for 1 drinks all the time and they cost 25-43 pesos, about $2.10 - $4.00 USD.