The falloff in quality in MPH programs is steep from the top-tier to the second-tier, and then stays level across the majority of remaining schools. This means, if you have the ability and finances to go to Hopkins, Harvard, UNC, UMich, UWash, Columbia or Berkeley, you'll get the best training in public health in the country.
If you can't hit one of those top schools, you'll get a very good to excellent education at most of the other ones. GW is not a top-tier school, but they charge top-tier prices. You'll do just as well at UMass (actually a better program) or Tulane (also dramatically better in IH) than at GW.
Remember, you're going into a field that suffers from an inherent LACK of money. Paying top-dollar for your education is probably unwise unless you're getting a product that justifies the cost. Who's going to pay back your loans? African kids with cholera?
I'm not criticizing you, I'm in the same boat. You're not an idiot if you do go to GW - they do have good things to offer. But after a few classes there, I wished strongly that I'd spent dramatically less at a state school for roughly the same education. Now I need the people I ostensibly trained myself to help to pay off my loans. Quite a dichotomy.
Remember, no one gets rich helping poor people except the Clintons.