I work in a "less-than-desirable" neighborhood. Haven't missed a day commuting since July 2006.

I've never had an issue. The thing to keep in mind is that the players are all interested only in other players. An old guy in hi-viz on a road bike with lights and panniers in the street is pretty much off their radar, except possibly as a curiosity, as in WTF? At corners where business is conducted, I make it pretty clear through my actions that I'm minding my own business, and in return am usually ignored.

Everyone else is the same as folks elsewhere. Over the years I've gotten to know a lot of the people along my commute--it helps that their address comes up on the computer at work--and I make an effort to be neighborly as I ride by. There's one group of young boys in particular that I'll take with me if I ever take up racing. As I round the corner shouts of "Hey library guy!" precede them all running out in the street as I go by. When I need a cheering section, they're the ones I'll ask.

I'll wave or nod to folks I see regularly on their porch, and always acknowledge other riders, especially can men. Although when asked, every bike I own was "$100, I got it on Craigslist." Interestingly, my Litespeed is pretty much invisible and an old yellow Trek--a bike I actually did get on Craigslist for $100--attracts the most attention.

The big thing is, that the bad neighborhoods are also home to good people. When near good folks, I act like I belong. When near the bad, it's clear I'm just passin' through.