USA Hostels (Sutter St), San Francisco, CA
USA Hostels has two San Francisco locations, both very close to each other. Guests are welcome to use the communal areas of both hostels, and from seeig both, I think Sutter is the better of the two (the other is on Taylor).
The hostel is about a 10 minute walk from the BART station, which takes you to and from the airport really easily. Be warned though, San Francisco is hilly, so it's a bit strenuous with your backpack on!
The staff on the front desk were always really polite and helpful, and you get given a map and stuff when you check in. There is lots of information posted around the reception area, and they often have trips and events planned for the day and evening, such as free walking tours, cheese and wine parties, etc.
The security is really good, you get given a code for the front door, so only guests can get inside.
Our room slept four, and we were in with another couple. There was plenty of room for all of us. There was an ensuite bathroom, which was always clean. In the rooms there were large lockers, which was really handy.
The communal areas were a kitchen (good, had stove and oven, microwave, fridge - but no freezer), dining area, lounge area (which became the bar in the evenings), and a computer area with sofas to lounge about on. They did a free pancake breakfast in the mornings.
The price was a little more expensive than other hostels we stayed in in the US, at $26, but it was still within our budget. Also, I hear that they have done two weeks worth of renovations since I was there, so it's can only be better!