I've toured for over 40 years in 9 countries, as well as extensively in North America. My attitude is similar to some of the other posters on this thread: 99% of the folks I ran into were good people. A very large percentage of them were great people and exceptionally nice to me.
I've cycled through many large cities, including Detroit, Chicago, Cleveland, LA, Boston, Oakland, San Diego, and San Francisco; without any major issues. A smile and a friendly "hello" go a long way even in sketchy neighborhoods. As a previous poster said, "situational awareness is the key". .
We carry these on our tours, and use them a lot.
Make up some of these for your tour; it is a nice way to say thank you.