Looks like tickets are available now for the Feb 16 game at Kezar Stadium (San Francisco) vs. Houston. (previously they were only going to be available at the door) http://purchase.tickets.com/buy/TicketPurchase?organ_val=25525&pid=6177727 This is a good move in my opinion. There are very few ticket booths at Kezar, so depending on crowd size, it could have become a logistical nightmare...
...and FYI if you want to avoid the shipping charges, I assume tickets are also available at the Tickets.com retail outlets. (I balked at the $15 they wanted in order to send my tickets via 3-day air) There are 3 outlets in San Francisco... San Francisco Giants Dugout 3251 20th Ave. (Stonestown Mall) Giants Dugout 4 Embarcadero Giants Dugout 24 Willie Mays Plaza (SBC Park) Full list of all retail outlets (from Fremont to Santa Rosa) is here... http://www.tickets.com/b2b/bay_area_outlets.html
That's 4 Embarcadero Plaza, in the shopping area near the Hyatt. The only thing at 4 Embarcadero is the Muni Museum.