I think instead of looking for particular named teachers, you'd probably be better off looking for beginning longarm classes. I know you said you're not interested in renting time on a longarm, but THOSE classes are ideal for what you're looking for. The teacher should teach you how to load it, how to adjust tension, what the machine's features are, some beginner quilting stitches and techniques, how to change the bobbin, etc. All of these lessons are invaluable for making a decision about whether you'd actually like the longarm process or not.
I've been taking classes as a way of test-driving new machines. You are right - testing them at shows doesn't really allow you to get a feel for the machine. Taking a class lets you put the machine through the paces, and you get to see how easy or difficult it is to do various tasks.
My personal recommendation is that you take a handful of beginning longarm classes from different teachers on different machines. Not all machines are the same, and you could have a bad experience on one machine or with one instructor that might turn you off from quilting altogether. So spread your exposure and have some fun!