Similar happened to me. I was at The Oaks Card Club on the border of Emeryville and West Oakland. I needed to get to BART, and it was just a few blocks on one street, so I thought I'd just walk. About half way down, a taxi driver actually pulled up without me hailing him and said "Man, what the fuck are you doing walking here? Get in and I'll drive you wherever you need to go!" It was either a great sales pitch or I was actually in danger and didn't know it.
My SF story: Chinatown, near the convention center. My wife wanted me to pick some stuff up while I was there. I had been there by day, seemed perfectly reasonable. I get done with the trade show, head over there near closing time to get what she wanted (perishable, so I left it to the last minute) and coming back I realized the character had changed considerably and it was a place I didn't want to be. I hadn't gotten a car because the hassles of parking made it a negative to me.
I think this was a bit before 7pm. It surprised me because I didn't expect the character to change that much while the stores were still open. The undesirable elements usually only show up once the legitimate people leave.
