I think a nice in between place would be either Santa Cruz, Monterey, or SLO. And don't whine about SLO being too far north for you SoCal folks, its farther from the bay area then it is from you guys.
I think this idea is great and will do everything I can to arrange to be there!!
Maybe look into a hotel sponsering it and giving discount rates to us to stay there and getting use of thier parking lot.
Would be nice to have some sort of schedule of events, maybe a tech session or two, and a judged contest with prizes in different categories. I think some of the budget should definately be for prizes and raffles.
EDIT: I just checked Mapquest and San Louis Obispo is 3.5 hours from LA and 3.7 hours from San Francisco. I think that would be the perfect mid point as its a great town (my sister went to college there) and you would get a huge college crowd showing up to see whats going on if there was some advertising for it. Think of how many people would want to do these systems if they could see them working in person!!
Plus, SLO is 10 minutes from a beach, plenty of camping, and if you hooked up with a local brewery to serve the beer alchohol would not be a problem!!