Both Clayton Cramer and the US Government Accountability Office ("Investigative arm of Congress charged with examining matters relating to the receipt and payment of public funds.") this summer estimated there are outstanding around 8 million licenses to carry concealed.

I can't speak for others, but I can say that almost every time I walk outside I've carrying a M1911 (http://en.wikipedia.org/wiki/M1911_pistol).

The only occasion I can think of where a private citizen would use a firearm in a public area is a city-owned gun range, or hunting on public land.