The management won't know if it was left by a stray or another visitor not associated with the trial, but the trial visitors will be blamed for it. Do not use motel towels or bath tubs to bathe your dog. Motel personnel do not appreciate the hair clogging their plumbing or the hair clinging to their towels upsetting other visitors to their facility. Bathe your dogs before you leave home. Make sure your dogs are flea free.
Many motels charge extra for allowing dogs so that they can de-flea the room.
Don't leave fleas behind after your visit. Don't leave your dog alone in the room. Barking dogs disturb other visitors and if left loose they can claw or chew their way through the motel furniture. Plan to take meals inside the room or keep your dog with you. If you must leave them for a short period keep them in a covered crate, hopefully they'll be quiet, and they won't damage the furnishings.