Boats are available to take you to see thousands of flamingos and for fishing. There are Mayan Ruins, abandoned haciendas and a variety of things to do. Casa de Heba is really best for getting away from it all. You can get by without Spanish, but bring a phrase book. It will be an excellent time to practice Spanish.
Prepayment is necessary.
If you want to see what other people have to say about my place, check out the Vacation Page at Rick and Kim Thomas's homepage. They had such a good time in Celestun that they dedicated a large portion of their homepage to their visit. They have pictures of the house, tours and such. Read, walk the beach, run, swim, pick shells, watch the birds and you will be content. Trips to Merida for shopping, to ruins, to haciendas, bike tours, birdand salt pond tours and fishing are available if you get restless.