We highly recommend booking a transfer ahead of time - travel day can be tiring, and long! Canada Transfers is a great company that we've been using for years.Click here to check them out.
You can always take a taxi from the airport and there will be many willing drivers outside of the airport. This can sometimes be overwhelming with everyone wanting to help you at once. Their prices can vary considerably, but offer the convenience of just getting in and going. Always ask the price, before you get in the cab!
Once at Puerto Juarez Ultramar Ferry, buy a ticket to Isla. There are departures from Cancun to Isla Mujeres every half-hour (on the half-hour) from 5:00AM to 9:30PM, then ferries at 10:30PM & 11:30PM. Note that most commonly, you will be sold a return ticket, so keep the portion that is returned to you for going home.
Now on Isla, you'll see the taxi stand is to your left. Waiting just off of the ferry, there are also Maleteros, a friendly local with a tricylce to carry your bags. They'll lead the way with your luggage for a tip. You can ask either to go to Hotel Las Palmas or the 'Mercado Municipal' is right in front of us.
If you're keen to walk to us, from the Ultramar Ferry: walk across the raised crosswalk (that goes between the Senor Frogs store and the 7/11) and continue down that street. It will open into the Zocalo (town square) On your left there will be 'the Express' this is the main grocery store. Turn left down that street after the groc store (the hospital will be on your right). We are about three blocks down, on this street (Guerrero) on the left hand side. You should be able to see our sign from about a block back and we're a yellow building. If you do happen to take a wrong turn along the way, ask anyone where the 'Mercado Municipal' is and we're right across from there.
Hint: get a Maletero, as described above, for a hand with getting to us and your luggage too!