If you know you're going to be doing laundry, definitely bring a roll of quarters and some detergent. I did 2 loads at Pop and was glad I had my own supplies. The coin machine was empty and people were scrambling around trying to get change at the bar or gift shop. Other people were complaining about how much the detergent cost. I was glad to have been prepared.
I put my detergent in small ziplock bags and put those into a larger ziplock along with some dryer sheets. It didn't leak or take up much room in my luggage. I'll plan on doing it again on our next trip (whenever that is).