I've heard many stories about clubs serving 'publicly' and the situations seem to depend on mostly on state law, and somewhat on interpretation by the organizer, local ABC officials, and whether they are paying attention. I would first start with a call to AHA to ask about California laws regarding homebrew at festivals. Some states explicitely allow this by law, some ban it by law, and most ignore it leaving it up to interpretation.
I'd be surpised if any club was interested in running a nano after the costs were accounted for. These also vary by state, but you'll need licenses, insurance, dedicated space, equipment. You'll probably get inspected. And then you'll pay tax on all that beer that you just want to give away.
You were right not to participate in the festival this time. If you're not pouring, then you can't promote your club and homebrewing. For me, that is the only reason to do this.