My wife and I were in Playa del Carmen for a week, and we came to The Coffee Stop 4 times. That should tell you something. I'm not a big coffee drinker, but my wife is, and she loved the coffee. My only tip food-wise is this: if you are there when they have chocolate cake... GET IT. Seriously some of the best chocolate cake I've ever eaten.
The owner, Paul, is what makes this place great. On our first trip, we expressed dissatisfaction with our resort's food. Paul recommended a whole list of places to eat. By the time we left town, we'd eaten at all of them, and every single one was delicious. Paul knows his food!
So basically, come for the coffee, stay for the conversation. Great little place!!!