There is a common scam pulled on cruise ship tourists and we fell for it. I speak Spanish well but was not familiar with Cozumel. We signed up for a Chocolate factory tour "Chocolates Kaokao Factory Tour" which we found here on Tripadvisor (not thru the ship). We walked out of the ship pier and across the street and a few blocks down just to get a feel for the area. We had considered renting bikes but after seeing the busy traffic and obstructed sidewalks, That seemed out of the question.
We saw taxi's lined up in front of a major hotel and took one. We had a print out of the address of the chocolate factory and the driver said it would be $10 USD. He took us down the same street till we got to a very commercial area and told us to walk a block. I should have NEVER let him drop me off anywhere except where I could clearly SEE the place we wanted to go. After walking around for a while some nice men in one of the many "Tours" booths told me we were very far away. He apologized and said this was not uncommon and offered to call the Taxi dispatcher for me. They also tried to get me to just go to another chocolate tour ( All of these guys get $$ for referrals) We thanked him and tried to walk it. We eventually found ourselves hungry and lost. We walked into a dentist office and explained our situation. They said right around the corner was a great Fish Taco "Mariscos" place and right across the street from that was the Taxi terminal!
After eating the most delicious octopus tacos, we explained to the dispatcher what happened. He did not bat an eye and had the nicest taxi immediately take us at no charge to the Chocolate factory.
Apparently the economy has dropped this year and desperate drivers will do this to make a quick turnaround to make another run without going too far out of the area. One person describes this as a mafia type situation here: http://www.cozumelinsider.com/TAXICZM
My advice is to have a map with your address & destination marked and to track where you are and not allow yourself to be dropped off anywhere else.