Im more worried about going out on a Friday or Saturday night in my home town than anywhere iv been in Cancun! Iv read there are some "issues" around the border areas but, as others have said, in Cancun just be sensible and aware of our surroundings as im sure you would be no matter where you were!? Agree with ToriB though, make sure you certainly DO get out the tourist area / hotel zone!!! I met a lot of people who were hesitant about leaving the hotel, let alone the tourist area, but its certainly worth it. I guarantee if you go you wont be the only tourist there, and part of the reason for visiting a different country is to experience what its like in the real world outside of the "tourist bubble" surely?