Well, if your are basing your "fandom" on the politeness of the fans than you licked the right team. The StL fans are the best.
There's a LOT of teams (in all sports) that have real obnoxious fans. The east coast teams are famous for this but some of the west coast teams are trying to catch up. When I watch a game from Oakland I'm amazed at how obnoxious the fans there are. Of course, when there's only 12 in the stands the obnoxious guy really stands out.
I've never had a BAD fan experience but the Yankee and Red Sox fans use to be pretty annoying at the Rangers games. A few years ago they would overpower the Rangers fans and just be obnoxious. Now, though, the Rangers fans pack the place every night and drown them out. Winning fixes everything....
I had a great time at Dodger Stadium a few weeks ago. No problems - everyone was real nice. Minute Maid Park in Houston is very fan friendly. I went to old Yankee Stadium a few years ago and had a GREAT time. A buddy of mine went to Fenway for a Rangers game and LOVED it. Of course - he didn't act like an obnoxious Ranger fan. That would just be ASKING for trouble.