Getty Mexico's Riviera Maya has been changed throughout the years from a sleepy backwater into a first-rate getaway location. And along with the tourist development, mobile specialists and digital nomads have actually flooded to towns like Playa del Carmen and Tulum. "Tulum has cornered the market for being eco-chic," says McMahon.

It's as stylish a destination as St. Barts, St. Tropez and the Greek island of Mykonos." Up until now, a 1,000-square-foot oceanfront apartment in Playa…