Hey there,
I got my MPH at SDSU (epidemiology concentration) 2 yrs before I started school. It was definitely a benefit, as it exposed me to a lot of interesting research, and I think it helped me stand out a bit during the application process. If you get the chance, i say go for it. It can only help you become a better med school applicant as well as a better doctor!
Good luck,
Greg
MSII
WesternU/COMP