I visited Sian Kaan with a tour group from Alltournative in a jeep in 8/01. It was really a fun trip although it had rained extensively the day before and parts of the road were almost totally flooded out. Luckily no-one in our group got stuck in the mud! Punta Allen was beautiful and we had lunch there and then snorkeling. Fantastic! We also explored some of the mangroves by boat. I highly recommend this trip.