Avoid Mexico like the plague it is. Seriuosly.

But if you are going, yes I've been to Cozumel. There is a whole strip right along the water that isn't too bad. Kind of a tourist area. Search for excursions given out, those are always a fun and safe way to travel around.

As for far as bars and partying? There are plenty of bars around, especially on that main road I mentioned. But I really wouldn't venture off to bumfuck. Mexico is not a nice place.