I just came back having used Cancun to get to Cozumel. Flew Southwest, then took Mayair to cross the channel. The scheduling on Mayair was great; timing worked just as advertised. They fly out of the FBO, so you have to take a shuttle bus (every 20 minutes) to get to the FBO terminal. Eat first; there's a private pilot's lounge where they MAY have sandwiches in the refrigerator, but there are tons of options to eat at the main terminal. Check-in is an hour before the flight, and the price for overweight (22 kg per person, not per bag) is very reasonable.
Equipment seems OK, though well-used, and there was some trouble starting on engine on the way back. However, they deboarded us, worked on it, and sent us on our way. Note that I'm reasonably familiar with aviation; once an engine starts, whatever made it hard to start generally isn't an issue any more, and they're twin engine airplanes, so there's a spare.
Looking at ferry options would also have been reasonable, as described above. You have to go to Playa Del Carmen, though.
Wendy P.