Fortunately, here in Nashville, we still have several thriving commercial districts and neighborhoods that retain a lot of local character (they're not overrun by franchises). I'm just starting to make some serious progress in one of them; it'll take years before I can begin to adequately explore the possibilities.
It's funny you should mention people stuck in traffic--I had actually planned to stake out a spot at a nearly cafe and shoot people in their cars while they were backed up in traffic. Due to laziness, I was a little late for rush hour, but the cafe itself provided some good opportunites.
I hate malls and fast food restaurants (don't like the smell, don't like the atmosphere, don't like the people), so I usually avoid them.
People's reaction to the camera tends to vary according to the area. The place I've been photographing a lot later is a favorite of students and artists in the area, so I don't stand out too much. I've had a few people ask who I was shooting for (they thought I was reporter). Another good area downtown is a real tourist district, so the camera won't stand out there.