Don't even worry about this residency crap. I've worked in teaching hospitals for well over 10 years now. Most of the residents I know in the hardest ones to get (Ortho, Neuro, ...) did a year of some other "less desired" (OB, Internist, Family Med) residency and then stepped in as a second year. Almost all of the highly competitive residencies require a year of crap first anyway. The only caveat is that you do need to have the right scores at some point. Long story short, switching from low to high happens all the time.
A random side note: a few of my friends that went to Caribbean (3-Ross, 1 AUC, 2 went somewhere in Mexico) are doing better financially than many of the docs that went to school in the US. In no way am I saying that money is the goal or that this is common, but it's certainly ironic.
1 went to Guada, transferred to Ross, became internist for a year, switched to ortho, then joint fellowship
1 went to Ross, then intern year for Obgyn, swithced to anesthesia, then cardiac anesthesia fellowship
1 went AUC, then intern year, physiatry residency, pain management fellowship
1 Ross, family med, then to anesthesia, then to pain management fellowship
1 Mexico, .........., Ortho, Joint fellowship
1 Mexico, .........., Ortho, Spine fellowship
I'm sure a bunch of people might come on here and fight with me saying that this is BS or it was a long time ago, but it's true and some very recent.
The most successful guy I know had a 2.4 GPA, 26 MCAT went to the Caribbean and now CLEARS six figures a month.
This will not happen to everyone, but I've seen enough people rise up that I know it can happen to anyone.