I am new to MT but was wondering what sort of questions I can ask the instructor before joining the place?
Well, you can start by asking when the instructor started, and how much experience he has with the martial art, and teaching in general. I mean, he could be a 100 year world champion, but could be the crappiest teacher in the world.
Maybe ask him if you could have a week trial? Just to check it out, to see if the class is right for you. (If you don't want to hurt his feelings and his class sucks, just tell him you can't handle the excersizes and you just found a new job that takes all your time, or something, lol)
P.S. I take Muay Thai, BJJ, and boxing all at the same place.