Prime rib galore roasting on spits at the Hot Luck Festival in Austin. Austin’s inaugural Hot Luck Festival of food and music in May attracted 6,500 “patrons,” according to a recent release from the organizers. “Patrons” is an interesting term. In broad form, it includes paying customers as well as those who don’t pay admission, such as guests, clients, sponsors and friends. At Hot Luck’s food events, based on my observations, there were a lot of non-paying attendees. In a follow up email, I asked Courtney Knittel, handling Hot Luck’s public relations, for a breakdown of attendance between the music…