If you want a party you can always find one here. If you want good food, the same. If you want good music, same. Just find your way to the Quarter or Harrahs and you will find some fun.
There is always something fun to do in Cozumel. This was my 4th visit so I didn't take an excursion this time, but in the past I have done the Mayan culture, Atlantis submarine, beaches and shopping and others. Have never been disappointed once there.