I've never stopped to look too closely at what's on offer, but the recently-expanded and renovated duty free story in Int'l Terminal G has a pretty big wine selection. That's probably your best bet if you're looking to bring home some California wine. Of course, you won't be able to use if you're not leaving the country.

Napa Farms a few doors down from the duty free also has bottles of wine for sale, though probably at inflated prices. They might sell to domestic passengers, though I'm not sure.