You might get lucky and find that there are a nice stack of towels in the condo, and you don't have to wash. Otherwise, I like to bring those detergent pod thingies or 3-in-1 detergent/softener/anti-static sheets:
Amazon.com: Purex Complete 3-in-1 Laundry Sheets,... Purex no longer makes them, but you can find some places online, such as in the link, that still have them. Take a few out, put them in a ziplock, and they pack nice and flat.