I would give it a miss if you can
It really is no better than OK.
The location is a bit dodgy and is not the cleanest. We stayed one night at the end of a tour and we had tried to extend our stay for the extra 3 nights we were in SF but thnakfully they were full and stayed in China town instead.
The Union Square location is slightly misleading as I can tell you it is not next to Prada and Gucci. There are a lot of crack heads about and is quite disconcerting.
The rooms were big enough but not very clean and the corridors etc could do with a good make over.
Breakfast was OK. You don't expect much in a budget place.
We are glad we found somewhere of comparable price in Chinatown, which although wasn't perfect was clean and you felt safe, otherwise our view of San Francisco may have been clouded.