Will be in the Dells late June.

[MikeS]

Oh, I wouldn't overlook Devil's Lake.  I have close to 400 dives in that lake and have never gotten the swimmer's itch and never saw a sticky goo.  It's a relatively shallow dive, so you get lots of bottom time on an air fill and the east and west shores have lots of rocks and friendly fish. 

And, yes Lake Michigan should also not be missed.  Closest would be Sheboygan or Port Washington.  Divers Delight charter does trips to both those places and Milwaukee has other dive charters as well.
I suppose you could expect around a 2 hr. drive from the Dells.