This is where is stayed when I went to Cancun. It's right on the beach and walking distance from all the night life, restaurants, and other local stuff.
http://www.marriott.com/hotels/trave...cancun-resort/
You don't need a car unless you plan on going out of Cancun and they have taxi's for that. They have buses that run all day and almost all night.
I will say this. During the day go exploring. Chen Itza , Tulum, etc...
Have fun