Anybody planning to go to Playa del Carmen must have a look at this handy interactive map put together by the guys at Playa[dot]info the website and forum dedicated to "Playa" living. Playa del Carmen is very easy to navigate as the streets are in a grid system. From the Playacar development right up to 38th avenue can be considered the "tourist" zone and this stretches back as far to the national Highway. Use this as your guide. To the east of 38 you have the "barrio" of Colosio which is were most of the local and orignal inhabitants live. To the north of the highway you have Ejido which again is a local neighbourhood without many tourists. There are also some new housing developments scattered on this side of the highway. Playacar 1 and 2 are the nicest areas to stay (and obviously the most expensive) and if you're not a local or Spanish speaker I would avoid Colosio and Ejido. In between 1st and 38 you will find accommodation to meet all levels and you are never more than 8 or 9 blocks from the beach as the roads running parallel go up in 5's. Most of the action is centred around 5th street, a boulevard of boutiques, restaurants, bars and tourist shops.
The interactive map can be found here: Interactive map of Playa del Carmen
The interactive map can be found here: Interactive map of Playa del Carmen
