Wow - that's cool! I made up some signs for my waterless car wash product that we sell and hang them in the windows. They are temporary enough so that if anyone has a problem with them, I can remove them. Haven't had a problem yet.
With some signage, you will get a lot of people asking about it. We met a guy in Florida that did window shades, and his business was booming. He would go to a park for a month or so, do his thing, then move along. Nice guy and it seemed that he did well with that.
You guys may be able to do the same if you have everything you need with you. Consider going to rallies as well. You would be able to sign people up while you dude handles the repairs. Could work well!
--kev