The warnings for tourism to Mexico is in regards to areas near the US/Mexican boarder....Cancun is nowhere NEAR the boarder.
I went a few years ago and it was WONDERFUL. We stayed in a resort just outside of Cancun, which was nice because it was a short Taxi trip to all the main attractions, but far enough out that we weren't in the middle of the spring break atmosphere.
I would suggest visiting "the market". It's basically a street market type place but you can get some really cool stuff. There is a little cantina in the middle of it with some of the best food and drinks.