Yes. USA is gun and gangster country. Very dangerous.
You know he's (kinda) joking, right? I mean, I'll give you that Richmond is a bit crappy, but it's right next door to Berkeley which is ridiculously expensive and fancy.
was thinking of going in mid to end September period but i think there is some big event going on during that period? planning to stay near san francisco union square area or along that stretch cause that is like the town area right? saw a few rooms going for maybe about $120 or less but the location is at the ghetto area which seems pretty unsafe.
September 12-14 is the Mobile World Americas conference in downtown San Francisco, so things are a bit jacked up on those dates, but after that is relatively reasonable.
Assuming you're not trying to travel on those exact dates, have a poke around on TripAdvisor; you should be able to find something relatively cheap and good; be realistic though, you're not going to get much for <$200 a night in San Francisco. I used to live around that part of town, so if you give us exact dates I can find and recommend a hotel.
by the way, is it walking distance from their train station to union square area? estimated about how long?
The BART rail network runs all the way from the airport to the CBD, and there are four stops within walking distance to Union Square: Civic Center, Powell (the closest stop to Union Square), Montgomery (nearly as close, and less busy), and Embarcadero.