I just moved to Huntsville from Rochester, MI.
I feel your pain, good luck finding cavers up there!
Detroit Urban Grotto - you are right, they will not accept new members, I got the same reply. They are active in the Fisher Ridge system still though.
MI Interlakes Grotto - goes to the little cave up north the...third? saturday of the summer months. http://www.flickr.com/photos/sunguramy/ ... 608559608/
You'll get bored with that fast. They don't do other trips.
Most all the other grottos in the tristate area even remotely close require you to attend 2-3 grotto meetings prior to any cave trips with them, so expect a 10-12 hour round trip drive for a couple hour grotto meeting a couple times during the weekenights first (who has time to take off for work, gas money to pay for that these days?!)
Your best bet bar none - St Joseph Valley Grotto. They accept brand new members, will take you on cave trips without ever needing to attend the meeting, you can Skype in to the meetings (2nd thursday of the month, 7pm), they are based out of Elkhart, IN. They are also on your way to the caving regions and will carpool. Grotto page: http://www.caves.org/grotto/sjvg/
It took me about 8 months to find them, but it is a very friendly group that got started because they were sick of the grotto crap in other grottos up there! So they are very different...$1/month dues, active caving, loves taking new people, etc. There are a couple hangout houses in IN too we'd stay at on trips down to southern IN to where the caves are.
Now...you'll notice that they don't have any 2012 dates on the site...the members kinda got sick of the same cave trips every year in Indiana so not many trips are being led this year, BUT there are plenty of active cavers just ask for a trip and you'll get one.
KY is a great place to cave, quite a few of the Michigan/Indiana cavers go down there regularly and you will meet the KY people. Lonestar Preserve is the place to stay in Ky! Speleofest is Memorial Day weekend, you'd be good to check it out and attend, you will meet lots of the cavers you will be spending time with, they have trips for newbies to advanced running, and vendors (On rope 1, amazing people) to get any gear you need and they'll let you try it out first before buying which is the best way. In fact I know of some KZoo cavers going down there who are always looking to carpool, I will shoot you a PM in a moment with their contact information. Good people. I've been where you are, stuck in a non-caving area and struggling to find decent people! Took me almost a year to find 'em, but they are there, and I'm happy to pass on the info to you so you don't have to go through what I did!