(This a composite of our adventures, representing a day in Playa del Carmen, Mexico, winter 2016.) One moment a sea of heads bouncing and bobbing down Playa del Carmen’s eclectic Quinta Avenida (5th Avenue), the miles-long, slightly undulating promenade paralleling the Caribbean Sea; a path full of hawkers spread evenly block after block, all selling various zip-line and snorkeling tours, excursions to Mayan ruins and to Cozumel, taxis to most anywhere in the areas of Cancun and the Riviera Maya. Beautiful people, restaurants, shops, and stores—low-end trinket to high-end Michael Kors and Victoria’s Secret—a busy Starbucks every other block. Nike and Puma, Sephora and Forever 21. Too, ultra modern malls,…