I travel a lot. I can't help you out internationally, but in the states, ask the desk if they are members of a gym. Do a little pre-planning and call them. If not spend a little time on yahoo maps. I have found:
24-hour fitness isn't bad except in Fontana, CA and Central Houston (medical district). Cost is usually around $10.
Balley's isn't bad either and half the time they don't charge you a guest fee.
Most of the local family fitness centers are pretty good and are cheap. Christus St. Whatever it is in that city.
Just do a little research before you go anywhere.