1. The morning of our arrival I received an email saying that they would accept payment in Mexican pesos (i.e., cash, no credit card). I didn't have the pesos but we went anyway, expecting to get to a cash machine. There's only one in Celestun, and it didn't work. They finally accepted US$.
2. We had booked and confirmed two beds. There was only one bed. They pointed out a sofabed (unmade) and said that it was the second bed (they pulled out the bed and finally made up the "second" bed.
3. There was no hot water in the bathroom sink (had to go to the shower faucet for hot water). The water from the toilet leaked onto the bathroom floor.
4. The receptionist was unfriendly and totally unhelpful.
5. Celestun clearly has a crime problem: ten-foot walls topped by barbed wire is the norm for the hotels beyond the town center, which appears to be safe.
6. Celestun's "biosphere" is basically mud flats. There is no "ranger station", no trails. The only "attraction" is renting a guided tour for 1.5 hrs to go see flocks of flamingos. There are other places in the world to see these birds (like, Florida).
7. Avoid this hotel and the town. If you want to see the flamingos make it a day trip from somewhere else (like, Merida).