Dave,
Robbie is right about northern Indiana being predominantly NSA. I have two ASA tournaments that I have been invited to umpire this summer. One is the Men's C SP state tourney in Kokomo, and the other is a FP tourney in South Bend. Either of those is an hour and a half drive. If I wanted to work NSA, I could have tournaments every weekend either in Fort Wayne or in Warsaw, both being 30 minute drives, in either FP or SP.
At the ASA school in Fort Wayne this year, I was being recruited by another umpire who works NSA to register for that organization, but having him tell stories about how he's doing games at 3:00 in the morning at The Dome in Fort Wayne because they don't have enough umpires doesn't exactly appeal to me. Heck, my wife doesn't like having me umpire more than a couple of times a week, and I can only imagine what she would say if I was coming home at 4:00 in the morning from umpiring.