Be safe...lol don't do anything that will mess up your future you have planned

1. Careful with the bugs! THEYRE LOUD!
2. Alligators come out sometimes
3. Watch carefully on weather channel. It tends to rain there.
4. Know which bus you are taking, because most of them won't help you find your Hotel (trust me =[ )
5. It's nice to walk when it turns to dark( 7 PM ish. its a really relaxing walk)
6. Never is a slow place.
7. Nude Beaches
8. Gets EXTREMELY HOT!! make sure to wear t-shirts and shorts. But to be on the safe side, bring some long sleeve shirts. Look up the local forecast BEFORE you go to Cancun.
9. Maids are up 24/7 most of them talk loudly lol its funny.
10. The ice cream there is amazing =] there are ice cream shops all around
11. Beggars lurk around.
12. A lot of bars
13. If you want your hair braided like a lot of people or tourists, there are like 5 or 6 places that are probably right near your hotel- prices vary little.
14. Watch for the cops. Theyre more strict =\
15. Careful with the wild birds lol
16. && Most importantly have your people who you came with by your side =]
You can get lost easily.
Doesn't matter what age, it's best sticking together as childish as it sounds.

You should definetely plan to have dinner at Lorenzillos (dinner for two 80 usd), they serve hte best seafood (specially lobster and shrimp) in Cancun.

After that I recommend to go to Cocobongo, one of the biggest nightclubs in Cancun.

Good Luck!!!!