It may be passe to say this but "Situational Awareness" is key to survival. We've traveled to New York City (Combat Commander .45); Oakland and surrounding Bay Area Cities (Combat Commander lightweight .38 Super); Detroit (Combat Commander .45 and Cobra .38 Special); Houston (Delta Elite 10mm). You get the idea; I don't travel within the US without at least one handgun. When driving my own vehicle I also have a Mossberg Shockwave 20 gauge loaded with #4 Buckshot to deter Car Jackers!
Why wife and I also travel internationally - unfortunately no firearms allowed but there are other options available - but once again (and mainly because of the family or friends we're visiting) we avoid areas where we either should not go but if we do - we exercise caution.