Like everyone said its DEFINTELY a good idea to learn on a beater. Thats one thing I probably would have done differently because I ended up beating up a nice bike. As far as the MSF course that depends on several factors. I don't feel like I really learned anything when I took it and that I wasted money on the beginner course and it would have been better for me to have taken the advanced course which is cheaper. You would have to get ahold of a bike first though if you want to take the advanced course bc they dont provide one.
If I were you this is what I would do:
1.) Get a friend to teach you on a beater bike and see if you like and how easily things come to you.
2.) If you decide you like it and want to persue it, but a 600cc bike thats either been down or is old (so its not too expensive) and use that while taking the advanced MSF course
3.) Ride that bike until, like Matt said, it becomes second nature. I know for me everytime I start riding my bike daily it becomes natural within a few days... then if I stop riding for a few weeks I have to get back in the hang of it... its just a matter of keeping it up and racking up some experience
4.) Then when you're ready you can get either a newer/nicer 600 or move up to a larger bike if you feel that you can handle it.