One tip for anyone taking a taxi in Cozumel, before you get into a cab ask the driver what the cost will be. If it sounds unreasonable, ask to see the rate card. If they "don't have one" or refuse to show it to you, don't get in their cab - they are going to try to overcharge you.
We made this mistake last week as we got in a cab at the Punta Lagosta port without asking the cost (but knowing the cost should be approximately $20) to get to Mr. Sanchos for our family of 4. We were shocked when we handed him $25 as we got out that he told us the rates had recently changed and it was $40. When I asked for a rate card, he said the rate was so new that he didn't have a card yet. We knew we were being messed over but to get on with our day we forked over the extra $15 and told him that we knew he was overcharging so there would be no additional tip.
On the return to the ship, we asked the taxi captain at Mr Sanchos what it should cost for us to get back to Punta Lagosta and were told $22. That driver was upset that the taxi captain shared the correct rate with us based upon a call to his friend to inform him in Spanish not to go to Sancho's - they are telling people the right rates and that he can't believe he's going back to the port for $20.
I'm surprised he assumed that just be because we are Americans that people in the car don't speak Spanish 😀