I don't think placing wet towels on the bed is a good idea at all. By the time they get to the room to clean it, the mattress could be damp and believe me they are not going to change out the mattress. I think removing the sheets is enough.
People are only putting wet towels on the sheets in the tub right? Not actually on the bed? I'd agree. Moisture in a mattress in that climate... DANGER!