driving and renting a car is really easy, we were there last year and stayed at dreams, we rented a car from there for a week and drove everywhere, it was cheap too, it really all depends on if you are happy to drive, the route is easy and once you understand the Mexican way of driving you will be fine, it should only take you an hour to do the drive. I don't know how much a cab will cost you, perhaps yoru hotel in cancun can guide you.

the other thing you have to remember is that most of the rental cars are not automatic.

hope you have a great holiday