Most all California RV parks have restrictions against RV or other vehicle washing due to drought water restrictions in place by the state government. Even parks that have their own lake water supply. I too have gotten the O.K. for the buckets and towel method, they just do not want to see spraying water. But then some of them have mobile RV wash companies advertising in the park maps, so they allow these companies ONLY to wash RV's on site. My preferred mix is to use a commercial car wash liquid concentrate in a bucket along with a scrub brush, wiping that up with a towel, and following with an application of Meguar's #50 RV Cleaner/Wax. Washing the roof this way can be a challenge, though.
Most big truck stops have an oversized mechanical/human vehicle wash that will accept RV's including towables. In fact, this is where I have sometimes gotten my dually truck washed there alone, as most all mechanical car washes do not accept dually wheeled vehicles.
Last week I cleaned out my reusable truck air filter, and replaced my fuel filter in the park. Once I found a spring-equalizer bolt missing its nut and 3/4 of the way out when I got into an RV park. After consulting with the ranger and telling him I wasn't going anywhere until this emergency repair was made, he said "No problem" and I fixed it. I had my welder come out to my space in the Fall 2014 and patch together my frame enough to tow the rig 7 miles to his welding shop with no problems from the RV park.