I didn't apply for dual-degree entrance, but will most likely take a year off in med school to complete an MPH. This is how it works at universities with both MD and MPH programs: you complete the first three years of med school, do the MPH in your fourth, then complete your MD in a fifth. Schools with great MPH programs that come to mind are Harvard, Johns Hopkins, U. of Michigan, Columbia (Go P&S! 😀 ), Emory, Duke, and Tufts. Both Duke and Tufts claim you can do both in four years; Duke allows you to do it during their research year (3rd year) in lieu of a research project. But remember, you can take a year off anywhere to go complete your MPH somewhere else. I have a friend who'll be at Stanford med in the fall, who's planning to take a year to do her MPH at Harvard.
Good luck! 😉