Bidness is bidness and if Sonoma pulls 10 other dancer/musicians while losing me and Alta Sierra gets me but loses those other 10, then there you are.
The last time I was there was summer of 2002 for a week-long Contra dance-oriented camp. The special attraction that year (and the one that made me decide to go) was the presence of Mona "Zydeco Queen" Wilson to teach dance and Billy Wilson and Motordude Zydeco to supply the music.
But you right, because, while it was a lot of fun for me, it was sponsored by the Bay Area Contra Dance Society and it was the most poorly attended event they'd had at the end of a string of dwindling attendance. And they counted on the Bay area dancers to keep it pumped up.
I see in my atlas that Sonoma is quite a bit closer to the bay than Fresno. Oh well, do what you gotta.
I haven't been to any of the camps, and in fact, I have had no formal or informal instruction of any kind, so it's a little hard for me to know what to suggest.
I suppose that whatever is done at the camps would probably work.