General

Are you going with friends or family? You can relax on the beach with pina coladas, take the speed boat thing to Isla Mujeres to do outdoor activities like snorkeling, and drink/go clubbing at The Strip at night.

if i were you, i wouldnt go to isolated places/far places/places with little tourists, especially if you dont look mexican. otherwise, have fun in cancun.

I've been to Cancun twice.

There won't be much fun unless you're 18.

Great place to eat sea food if you're into that

The general gist of what you do in Cancun is relax on the beaches during the day, then go out and drink as much as you can in the evenings, with some mexican cuisine sprinkled throughout the day. Lots of spring break-y type bars out there (popular one that comes to mind is Senor Frogs). You can do other stuff as well like go snorkling, fishing, and stuff like that during the day, but the night is left to party. If you actually want to learn stuff/go see the culture, I suggest a day trip to Chichen Itza (mayan pyramid--pretty cool, I'd say this is a must go to spend a day here; you'll be back by evening to go out), and one day you can go for lunch or something into actual Cancun (away from all the shops, hotels, clubs).

Honestly, when I go to Cancun, I go there just to relax so I stay at the resort. Package with prepaid food + drinks + entertainment = happy relaxed me.

A place like that is really just for relaxation imo. Who are you going with? If you have siblings go to the beach with them.

Do, just that.