Cancun was a family vacation for us so it was a little different from our normally nomadic travel style. Instead we spent most of a week in one location - Punta Cancun Towers, seen here from the water. They are centrally located right at Punta Cancun (the northeast corner of the beaches) and have very nice facilities. They might be a little on the sterile side but you're not really insulating yourself from "the real Mexico" on the beaches of Cancun.
This is a view out the other side, across the point. Off to the right of this picture are malls and night clubs and cheap t-shirt shops and everything you'd expect to see in Cancun. We spent most of our time here without a car. Buses run up and down the beach road and into Cancun centro. We took one trip into central Cancun and were a bit disappointed. Sections of the city, especially around the bus terminal and markets are just as tourist-oriented as the beaches.
Ok, the pools and the view at the P.C. Towers are worth it. Especially that infinity pool on the edge of the ocean. That wasn't the edge of the ocean until Hurricane Wilma took away these north-facing beaches.
Here is the aforementioned view. That line of white dots on the horizon to the right is Isla Mujeres which gets its own webpage. The line of white dots to the left is mainland Mexico. The water looks pretty good from here but visibility near the shoreline is not particularly clear.
The one thing that surpassed our expectations was the food. We didn't expect we'd be able to find traditional Yucatecan cuisine but outside of the malls there are several good restaurants around. Besides Merida-style food we also found good Oaxacan and seafood restaurants. This is the shrimp salad from Mocambo, just next door to our residence.
We rented cars for the last few days in Cancun (and beyond). All of our day trips out of the city to both Isla Mujeres and Tulum were extensive enough to be the subject of their own pages.