SB always gives solid advice.
He has a cheap book available for accommodations in Mexico. You should ask him about it, really.
The mountains on the Pacific side are so close to the coast that everything runs right to the ocean, and fast.
Just for typing sake....the low section of the road to Palenque is bordered on the east by a small section of mountains that creates a different watershed than for the Tenosique area.
I wonder what the NW Peten is like. The Usumacinta, San Pedro and Rio Pasion must be some roaring btches down stream.