Blizzard Beach has a decent shower/changing facility. I used it last year because we had a night flight home, so we spent the day at BB, then showered there, got dressed and went right to the airport.
In the locker areas there are a few outdoor shower heads activated by a pull chain. Useful for getting the sand off your feet but your feet will pick up a bit more sand as you walk into the changing room.
Thanks! We'll be at Blizzard Beach the day I'm thinking of going out to dinner before we head in for the night. Just wanted to make sure we could clean up first.
You'll be fine. The facility is adequate for those purposes. I did feel out of place, though, leaving the park with fresh make-up and fully dressed! Everyone else is wet, hot, and sweaty leaving.