We use this service often. It's the least expensive form of airport transportation. There are two routes:
Route #1 (see pink line at right) goes direct from the airport, north to downtown Cancun (it does not go to the beachfront hotel zone). Route #2 (see yellow line at right) goes south to Playa del Carmen. The bus makes a quick stop along a highway frontage road to drop off passengers going to Puerto Morelos.
Price: 62 pesos (about $5us) plus taxi fare from bus station to hotel.
Departure times (subject to change): 12:30am, 9:20am, 9:50am, 10:20am, 10:50am, 11:20am, 11:50am, 12:20pm, 12:50pm, 1:20pm, 1:50pm, 2:20pm, 2:50pm, 4:20pm, 4:50pm, 5:20pm, 5:50pm, 6:20pm, 6:50pm, 7:20pm, 7:50pm, 8:30pm, 9:15pm, 10:15pm, 11pm, and 11:30pm.
Price: 146 pesos (about $12us) plus taxi from bus station to hotel.
Departure times (double-check times at http://ado.com.mx): 9:15am, 9:45am, 10:15am, 10:50am, 11:30am, noon, 12:25pm, 12:50pm, 1:15pm, 1:40pm, 2:05pm, 2:30pm, 3pm, 3:30pm, 4pm, 4:25pm, 4:50pm, 5:15pm, 5:40pm, 6:05pm, 6:30pm, 7:10pm, 7:50pm, 8:50pm, 9:50pm, and 11:30pm.
Price: 84 pesos (about $7us) plus taxi from highway drop-off to hotel—40 to 100 pesos ($3.50 to $9us).
The bus station is only one block from the waterfront. Walk toward the beach and turn right to find the ferry dock. Bicycle taxis are available to handle your luggage.
Catch a first-class bus to Tulum, or catch a taxi to Puerto Aventuras or Akumal.
(in Spanish): http://ado.com.mx