My wife and I spent two days and three nights in SF on a vacation in March 2003. We had a nice room at good priced hotel right off Mission street.
It was bad enough in the day but after dark it was AWFUL! I was afraid to even walk a few blocks to go to a grocery store and get beer!
And during our visit they were having alot of their anti-Iraq war protest so I had to bob and weave driving through their already confusing streets trying not to hit again hippie protesters. Okay, I didn't try very hard! lol
RE: We had a nice room at good priced hotel right off Mission street.
Your biggest mistake, right there. With the exception of a couple blocks near the Embarcadero, that street is nasty.