Most of my colleagues have an MPH. It does help... in that career field. Are you focused on public health as a substantial part of your career?
Please excuse my shrewdness, but is this simply filler for an application for school or work? Adding MPH next to your name to work as a PT doesn't do much of anything if you plan to work strictly as a practitioner.
If you plan to work in public health and that is your main focus, then by all means. It would for sure be worth it. Does it make you more valuable as a PT and potentially earn more money? I don't know... I'm not a PT or an employer so I can only speculate. Wouldn't imagine it would...
Now this is for the company I currently work for, so take it with a grain of salt, but usually a MPH is combined with MD and those individuals direct health initiatives for the company. I have no idea how an MPH/DPT would fit into our community health structure. I'm biased towards PT but I think that there is an epidemic of poor movement, posture, children tearing ACL's at an increasing rate with our sedentary culture so I think there is a place for them. Personally I love the idea of MPH/DPTs in public health.