I flew to Bamako through Casablanca in January and it was fine. Flew on Royal Air Maroc from NYC and had a 15 hour layover. They gave us a hotel room in downtown Casa and we had a nice day hanging out, eating DELICIOUS food and enjoying a little stroll through town.
It is a little weird because Air Maroc doesn't tell you anything, so we kind of wandered around the airport for awhile before we figured out there was an office set up to arrange lodgings. I think they do it for any layover over 12 hours. It definitely helps if you speak french at the airport... but once you get to the hotel, they spoke english.
Flying out in the middle of the night is a bummer. All the flights from Morocco to Bamako leave at 11 or so and get in to Bamako at 3am. When you arrive, there will be a great crowd of people hanging around outside trying to get you to hire them. I think it would be much better if you had someone arranged ahead of time.
The guy that runs Rootsy Records puts people up for a low fee ($30 a day, I think, including home cooked food.) He will also arrange lessons for you if you want. I would guess he'd figure out about picking you up at the airport, also. His website is:
http://www.rootsyrecords.com/A friend stayed there a year ago and her feedback was that it was small and pretty spartan. (Dorm style rooms, with bunkbeds.) She also said it was a little claustrophobic because you are in a compound in the middle of a residential neighborhood and there wasn't too much going on in the immediate area, so folks didn't really go out on their own. I think that may have had more to do with the fact that she was only there for a couple of days. I think if you were going to stay for a few weeks, you'd certainly get to know the neighbors and start to get to know the neighborhood enough to feel comfortable wandering around on your own.
When you do go to Mali, I HIGHLY recommend the National Museum in Bamako. It is stunning. The artwork is simply gorgeous. It was one of the highlights of our trip.
If you want to connect with teachers, I have a few friends I could probably set you up with. I worked with a great dance teacher while I was there. I could probably also hook you up with a drum teacher... or dun duns.
As far as cost per teacher... I am not sure because I paid a lump sum for the whole trip, but Jeremy at Rootsy says folks are charging about $10 per class. That seems like a huge bargain.
I wish you luck on your journey. I LOVED Mali and can't wait to get back. It was one of the best experiences of my life.