You don't mention where you will be staying, but I can offer you the following information. I returned from POFQ less than a week ago and this information was included in the "Welcome" packet we received when we checked in.
"Coin-operated washers and dryers, as well as change machines are located in air-conditioned comfort at each pool complex, excluding Ol' Man Island. Vending machines offer laundry soap and bleach, beverages and snacks. Folding tables and carts are available."
Since no hours are specified, I am assuming that the laundry facilities, at least at POFQ/POR are open 24/7. Laundry service is also available.