US quarters are a must. As noted, there are machines in each laundry facility; and if you find one not working, just use the phone in the laundry and they will bring change. Nope, I am not kidding! This happened when we were at POP this January. Machine ran out of moula, and CMs were happy to correct the matter.
US quarters only.... made the mistake last year and machines won't even accept it.... unlike up here where any vending machines take everything.... slugs included..