We did this a couple of years ago. We booked directly with a Cozumel cruise excursion site (not sure if I am allowed to post the name or link on here). We had a great day! The dune buggy was a stick shift. I don't think it was in the best shape but it was fine. My friend had to drive it until we were outside of the city limits then our guide took over the driving duties (that was our choice). The guide was really nice and wanted to be sure we had a good time. We went snorkeling, visited a small ruin, saw some crocodiles, went to a lighthouse, went to a beach (on the undeveloped side of the island), had lunch, shopped, and went to a tequila place. There was a cooler in the back of the buggy with water and beer. We weren't in a caravan of dune buggies--it was a private tour so we could spend as long or as little time as we wanted at each stop. I don't remember the exact price but it was fairly inexpensive.