A buddy of mine knew of a group in Lansing. He has not played with them but tracked down some Intel on them.
They play on the first Saturday of the month at Summit Comic and Games in Lansing, MI.
I live in Traverse City and irregularly run in Bay City and TC. My play group is scattered around the state so that's why I run in Bay City mostly. My group predates BT, CMU alumni from the early 80's.
My buddy lives in Kalamazoo and is involved with a couple of large groups in Grand Rapids and Kalamazoo. These groups play regularly I believe.
Hope this helps if you have not found a group. Also anyone else interested in any of these groups I can get more info. Everyone is open to new players.