I think it could be a great idea. I think it'd be best to be mobile with it, and just set up where people are hot and dry, and want something cold and wet (wisdom from King of the Hill).
My first trip to California I went to Monterey in December, and every restaurant I went to had the normal soda options, as well as a pile of oranges and a juicer. Rather than trying to sell the equivalent of tropicana OJ, what you got was frothy, foamy, pulpy, and 9 years later still one of my favorite things ever.