As an owner of an Optoma Movietime DV10 (an All-In-One projector with DVD player and speakers), I've projected on all sorts of surfaces. If the side of the RV doesn't have all kinds of stickers on it, the picture will look good (relatively speaking of course). The textured side won't make that big of a difference. If you hang a sheet on the side, it will look even better. High thread count sheets work the best, but anything goes in a pinch.
The other thing you have to remember is that you'll need a video source and a sound source. A laptop can provide both as long as it has a video out port and the projector can accept it. Of course, an All-In-One like the Optoma or several Epson models is even better. I literally can take the projector out of its case and be watching a movie in under 5 minutes. And everyone loves a movie on the big screen, especially out in the wilderness.
One important thing - Don't forget an extension cord.