Hope you guys have a great time! Foursquare was super helpful, so don't be a slave to this list; definitely Foursquare your away around. But don't miss El Fogon and Los Hijos de la Tostada.
Beside the specific recommendations below, you should spend a lot of time just walking up and down 5th Avenue (Calle Quinta Avenida); it's pedestrians only and where most of the spots are. We found the whole area to be safe, so feel free to explore.
You might want to spend an afternoon visiting one of the cenotes (the partially underwater caves), too. They're really pretty to just swim around it. The one we went to was by Tulum, so pretty far from PdC, but I think there are a bunch near Playa del Carmen if you just look on [tripadvisor](https://www.tripadvisor.com/Search?geo=150812&searchNearby=&pid=3826&redirect=&startTime=1540834269706&uiOrigin=MASTHEAD&q=cenote&supportedSearchTypes=find_near_stand_alone_query&enableNearPage=true&returnTo=__2F__Attractions__2D__g150812__2D__Activities__2D__Playa__5F