Most people everywhere, including criminals in bad neighborhoods, have alot more on their minds than a passing bicyclist. If it makes you feel better, get some data on the types of crimes committed in the area you are worried about. I would bet that there's not alot of stranger crime and that most of it is between people who know each other. Besides, the more you become part of the neighborhood, the more people will start looking out for you (in a good way). I experienced that over six years as a commuter in what many people would consider unsavory areas of Washington, DC. The good people, however, far outnumbered the bad and I never had any problems except one afternoon when some kids tossed a rock into my wheels. They were not out to rob me, just being kids and being stupid--just like in every neighborhood.