I would think they are pretty receptive to the idea and some integrate it into their curriculum. However, I suggest you do the MPH after you get in to medical school and finish residency. You don't know what you want to do in the future, since this will be 8-10 years down the line. If you still decide to do an MPH, you can pursue it as a doctor or during fellowship (occupational/preventative care, some programs will even pay for it). I had taken public health classes with two physicians trying to get their MPHs. So don't worry about it till later.