I live in NYC. Maybe this is different in the suburbs. Nearly 100% of the people that approach me are trying to get something from me. Scam me, get me to sign something I don't want to sign, get me to donate my money to save the dogs/children/etc.

If someone on the street tries to talk to me, I try to avoid even looking at them or acknowledging them. They'll use that as an opening. Just keep walking.