http://www.mototireguy.com in San Francisco (south end of the city).
He charges $22 each for a mount & balance.
Plus $20 if it's on the bike.
Plus $2 for legal disposal.
You can have tires shipped directly to him from several reputable tire stores.
He lives in a residential neighborhood, and schedules 1 appointment per hour.
He won't work on loud bikes, because he likes his neighbors.
He's done several tires for me, and more for friends. Good guy, super quick service (15 minutes per tire), and appointments only, so there's no waiting.