Lotsa Cancun info here:
Vacationing Here - Message Index
Been there five times now, (and Cozumel twice) have stayed at the Ritz Carlton (Freaking NICE!) and three other places over the years. (forget which places, but nothing special)....
Bought a timeshare last time I was in Cancun, right in the heart of the Hotel area (couple doors down from the Rainforest cafe)...<slaps self for not going back since>....
I much prefer Playa del Carmen and Cozumel, cause I am a scuba diver....the waters there are FAR superior to the Cancun waters (for scuba that is)..
Read up on that board, they give you TONS of 411 on local stuff. I love taking the buses around, you can get to the 'downtown' part of Cancun for cheap, and be sure to check out Mercada21, for the cheapest touristy stuff you can find anywhere....its a huge outdoor flea market basically.
Of course, check out the Maya ruins....and isla mujeres is cool too.
Its nice to speak spanish....the locals dont realize I am nearly fluent in spanish, and when a white ass punk like me starts asking serious questions to them they have quite a look on thier faces.....I often find myself translating for random people, and of course; I mention in Spanish that the other person is a fawking idiot....
enjoy your trip, give the locals my angry salute....that should go over well for you.