Our experience- Counters opened 3 hours before flight time, so around 10:45 or so. Got $30 food vouchers/passenger via email, a couple of hours before check in opened. Voucher good for the 2 locations mentioned previously- Tomokazu and Napa Farms market. We had a nice dinner in San Mateo area prior to heading to the airport. Used the vouchers at Napa market, which was overpriced to begin with and that $30 does not get you much. Bought some dessert and drinks and spent the rest on some overpriced chcocolate for gifting. You can only use the voucher for a single transaction, so make sure you use up all of $30 or even go a little above and just pay the balance with cash/cc. Any money left on the voucher is lost.
Hope this helps!