As noted there are several Truck Wash places.. HOWEVER use of high pressure guns on RV's is ... Not recommended (They can push water straight through the seals on slides, compartment doors and windows)
BLUE BEACON, from what I understand, actually trains their workers in how to properly wash an RV.. other places you take your chances.
I know BB did a very good job on my rig... Another Generic, Truck wash did a good job too but BB did it better.
Some places have professionals who bring mobile hardware to you.
Las Vegas has both a BB and at least one mobile service.
ALSO.. Many RV parks have a bulletin board where people put small ads for goods and services they have for sale.... Many of those boards have at least one mobile RV wash service on them. You park, they come out and clean your house (Well the outside anyway).