Like the others have mentioned definately take a course. Some have bikes that you use and others let you bring your own bike. I think there is a fear about buying to much of a bike to start with. Honestly if you take your time and slowly work at it you shouldn't have an issue. If you take small trips around your neighborhood you can get the feel of it rather quickly.
If you went with a smaller bike you might regret not getting the one you wanted. If your not really worried about trying to resell your starter bike then get a starter and move up to the one that fits you.
Good luck.
