I haven't ever been to Progresso but have been to Cozumel and did the Playa Mia Deluuxe Beach Break. It was a lot of fun, they offered free buffet lunch, underwater replica mayan ruins, water trampoline, jet skis, parasailing, iceburg climbing wall in the water, showers, massages, etc. The beach was beautiful.
I was reading somewhere that the pier they used to use will be reopened by then, it had been closed since the hurricane a couple of years ago and is now reopening and it was a really good place to shop.
On the jeep rental, I would be leary....I read on one of these threads about a couple that rented one and when they came back they accidentally bumped the taxi in front of them and it barely even scraped the taxi's taillight and he made a really big fuss and the police came and took the couple to jail and told them they had to pay as best I can remember somewhere in the vicinity of $800 and they had even taken out the auto insurance (which did them no good because they were after cash) finally they let the wife leave and go to the ship to get money and she had to scrape together the cash from their bank card to get them out of this mess. All the while trying not to miss the ship.
I was thinking about doing an excursion in Cozumel this time that isn't on Carnival's list, but I am also scared not to do a Carnival one, because if you go on Carnival aren't they responsible for seeing to it that you get back to ship on time and if you take another one is it worth the risk of getting in a jam and not getting back there? I am so undecided.