It is not practical. SF has lots of hills, and lots of stop and go traffic. That stated 35mpg would probably equate to 20mpg or less in SF. In the last couple years, I have only seen one Volt in SF. There are lots of Priuses and other hybrids that cost less than half the price of the Volt in SF. People here tend to go for compact cars that fit in tiny parking spots, as parking is scarce. The money you save by not buying a Volt can fill a lot of parking meters.
For its size, it's a very heavy car. Going uphill would thus use a lot of energy. Some of which may be recouped under braking going downhill. (I presume it has regenerative braking.)
But stop and go traffic is perhaps the only situation where an electric car has a real advantage: Electric motors do not need to idle.