I had the chance to go to a game in St. Louis a couple of weeks ago, and you're right. The Cardinals fan base is almost 100% white, suburban, well-behaved, and middle-class - a stark contrast to the residents of the city itself. It looked to me like Cardinals fans come downtown for the game, then get back out as fast as possible (LOL!) The Mets fans, in contrast, have all that New York attitude (and the vulgar t-shirts that the Fox cameras have to pan quickly away from).
In San Francisco, believe it or not, Giants crowds are more like the St. Louis crowds - largely white, suburban, upper-middle-class, and well-behaved. Baseball has left the blue-collar fans to the NFL. ;)
go there when they play the cubs, its different ha