Can't beat ST - Mal Pais, plenty of stuff to do and less of a chance of getting chewed on by a jungle skeeter with dengue. CR has some pretty high dengue rates depending upon where you are.
That's because it's tropico seco. Dry. 22% humidity. your sweat would boil off cooling you naturally We camped at Playa Carmen for a few weeks and a couple hours after the sun went down, it got kinda chilly. Of course those hours in between were like being in hell.