I can say from living in Orlando for a year, that it is an angry city. I remember hearing a lot of stories on the news of random assaults and extreme road rage involving shootings for small traffic inconveniences.
I can also say from living in Detriot (#3) for a year, that it's filled with unpleasant and up-tight people. (SE-MI mob feel free to disagree) But now that I live in Nashvile (#5), I can't say that I think it's very angry at all. Pretty nice folks in general.
I would pretty much assume that citizens of any 'big city' will have a certain amount of stress due to traffic, because traffic sucks in all big cities. Orlando's traffic sucks just as bad as it does in big cites, but it's not a big city at all. It's population is about equal to, or even slightly less-than Fort Wayne IN. People may be angry because it's hellaciously hot and humid, and their roofs get blown off once a year by hurricanes.
Or maybe because they have cocroaches the size of small children.