I will assume you can at least get to the Cancun Airport.
If it's your first time here, to get from the airport to the ferry, then I suggest you useBest Day Transfers...
Make Best Day reservations in advance. You can take a cab, but it will cost $65 one way!
go to their website to book a reservation or give them a call at 800-593-6259. If you decide to call them they usually speak pretty good English. as of April 2010, their rate is 17.00 per person round trip from the airport to the ferry at Gran Puerto at Puerto Juarez.
When you exit Customs, there will be a bunch of folks trying to get your attention trying to sell you Time Shares. Just put your head down and GO OUTSIDE!
when you get outside just look for the Best Day uniformed folks. Always nice and always there. if for some strange reason, they are not there, you might wanna give us a call at 303-952-0232 or on a mexican cell at 998-183-99-71 and we will figure it out from there, but no worries, Best Day is always there.
other shuttles include: USA Transfers - 998-914-0290 (bummer they don't have a US number...they really should...one reason i don't recommend using them. or you can call Cancun Valet.
When you arrive at the ferry, buy your ferry ticket - I suggest a one way ticket (at 70 pesos each way as of April 2010) that way you won't have to keep track of a round trip ticket...you can always buy a one way ticket on the way back. Ferry ride on the Ultramar ferry takes 20 minutes and runs each direction every 30 minutes beginning at 6:00AM until midnight.
When you get to the other side...WELCOME TO ISLA MUJERES!
Most likely, you will need to take a taxi to Casa Roca Caribe. Before you do that, you might wanna go to HSBC for some pesos. once armed with pesos, the taxi stand is right next to the ferry docks... too close to miss.
Most taxi drivers either speak little or no English and will not know Casa Roca Caribe without directions...so you will need to be able to handle that.
Directions in English: "We are going to a house very close to the Mango Cafe. When you approach Mango Cafe (about 2 miles south of the ferry, you will see Mango Cafe on your right) ...go straight for one more block and take a left on street Emiliano Zapata (there is NO street sign there. Casa Roca Caribe is up the block and is a two story house on the right. it is hard to miss, there is a big blue sign on the house."
Directions in Spanish: "Vamos a una casa muy cerca del Café Mango. Cuando se acerque a Mango Cafe (aproximadamente 2 millas al sur del transbordador, podrás ver Mango Cafe a su derecha) ... Ir directamente a una cuadra más y girar a la izquierda en la calle Emiliano Zapata. Casa Roca Caribe es el bloque y es una casa de dos pisos de la derecha."
The taxi ride should cost you only 30 pesos (as of April 2010) plus 10 pesos per bag. When you arrive, just pay him and don't allow him to charge you more than that. If he does, we call it a "gringo tax"...