I would advise no - according to my friends who went when we were on the Galaxy - they said it was smelly, depressing and they would never go again. Be advised too - any trip to the Mayan ruins is about an hour drive in not well air conditioned buses!
I have heard reports quite differantly! Anyone have any FIRST HAND information or thoughts? As for trips to ruins, all the buses I have ever taken on tours were quite nice. Local buses were the pits.