The small, rustic beach strip of Tulum is now THE hotspot along the Riviera Maya, the stretch of the eastern Yucatan Peninsula coastline (which includes the other popular but more developed resort town of Playa del Carmen), popular for its pristine sand, (bikini) yoga retreats and full moon parties. Some would say it's the closest thing to Ibiza we have this side of the Atlantic (at least, the bohemian, carefree side of Ibiza), where days can be spent relaxing and exploring the natural beauty of the sea and the freshwater cenotes, and evenings eating delicious food and joining in the upbeat nightlife.
JK and I came for a few "adult" days away in August 2013 and had a blast - keeping the summer heat in mind, we booked into Be Tulum, the swankiest hotel in the area (ie, the only one with round-the-clock AC, hot water AND pool) and had a full week of beach, cenotes, eating lots of tasty local and international food and taking a terrific cooking class at Alta Mar.
Ceviche, El Camello
Dos Ochos cenote - no artificlal lighting here!
Ignore the plastic-wrapped plates, Honorio's tacos are delicious (just check out that crackling!)