I too commute into a very bad part of town from a very nice part of town (relatively speaking). I've lived in these "bad part of towns" all my youth. Follow Cfibers advice: look unimpressed, like you belong, wear shades, and if anyone ever talks to you (doubtful), short answers and nods work well. But keep pedaling. Ignoring, or outward display of "weapons" only encourage rudeness and possibly worse. Just chill, keep pedaling, and ride a subdued bike. If the homeboys ever ask for your bike, give it to them. If they say "nice bike," say "thanks," and keep pedaling. If your commute is rush hour, I'd say you'll be fine. There is some stupid sense of honor among the typical Ana-crime gangster, and that generally means leaving "civilians" alone--but there are no rules with the meth heads...