I live in a very safe neighborhood but I keep a watchful eye on my surroundings and I am usually armed not out of fear but a love for guns and the 2nd Amendment. I would highly recommend self defense and/or firearms training. The best defense when walking in a crowded city is a good offense. Never be afraid to ask someone who is approaching you to STOP and don't let someone who doesn't fit in or makes you uncomfortable out of your sight. If you really want to feel "marked" walk down Canal St. in NYC. I'm not sure that the street thieves in Detroit compare to some other cities.