I don't think that just doing an MPH degree and then getting a job with it with a 2.7 undergrad GPA will be too much help. You need to show med schools that you can do well in science classes, not MPH classes. If you're graduating with 2.7 GPA (or even around 3.1-3.3), I think you need to raise the GPA with upper level science classes...that is, complete a Post-Bac Program or get a GMS degree (several schools over it, such as BU). Overall, with 2.7, it'll be hard getting into any medical school, be it allopathic or D.O.