About a 20 minute ferry ride from Cancun is Isla Mujeres, a beautiful little island for someone who wants to slow down and get away from things for awhile.
You get around by golf cart, moped, taxis and by foot. On the south end of the island is a nice park called Garrafon Park.
There are some ruins, dedicated to a priestess.
Watch your step, the paths can be really slick. No climbing on the ruins.
Some great walk ways with the resident iguana watching you as you walk by.
A great little reef close in to snorkel around and watch all the fish.