I've received quite a few questions recently on the Student Doctor Network about residency, clinical medicine, and careers in non-clinical medicine. Here's the bottom line: you'll have many more career opportunities if you complete a residency and become board-certified in a medical or surgical specialty. Of course, if you're stuck in the middle of a very long residency and you really don't enjoy your work, then you may want to consider switching to a shorter one. You can still find opportunities if you don't complete a residency, but make sure to do your research so that you understand your options.
Also, you don't need an MPH or an MBA to succeed in the non-clinical world. Although these degrees help, they aren't necessary.