Actually, looking at Google maps, there is a truck wash just before Kingman at exit 66 at Petro (truck wash looks like it is way in back after driving through the area where the trucks park) and at exit 59 by Love's (same side of freeway, just across a little road from Love's).
Don't know if these are self-serve.
2002 Itasca Suncruiser 32V
2012 Suzuki Grand Vitara