I think you're in a really interesting situation (in a good way). I've only taken classes in medical anthropology, and won't start my MPH until the fall, so I can't speak from first hand experience about your concern. I think in your situation, they would really appreciate and respect your background and the fact that you have a bonafide interest in going into public health since you've spent post-grad years doing culture vs. biology studies with your anthro masters program. The one thing that might be curious to them is what you're looking to do with an MPH that you cannot do with a anthro masters. I would think you can never have too much experience; it's not quite like law school where they some times say you should forget everything you learned about law before you start.
I think others can weigh in on the potency of an MPH degree and the symbolic value of the title. Depending on what sort of career you want, I would wonder if you can get the education and experience you need through your anthro master's program without pursuing an MPH? If you've taken a lot of core public health courses already, is there something particular that your anthro masters isn't going to give you? From applying to public health schools I've learned that they appreciate a well articulated vision of what you want to do more than anything. And you can articulate that vision best by emphasizing what you have learned in your masters courses and how that would complement their MPH program. I agree that medical anthro and health behavior public health share some territory, but I think a lot of anthro grad students are mostly interested in academia and teaching at the university, whereas health behavior MPHers are primarily interested in the not for profit work, administration etc. Hope this helps.
