If I were you, I would just start. I did some of my training there a few years ago, and thought it was fine. If you really aren't liking it there, then you can always try to transfer. I am pretty sure that you can get any residency you want if you do well enough at any medical school & the boards. The main place it could matter, is if you want to go into academics, it may be preferable to go to a prestigious medical school. But otherwise, I think it's better to just get started.