David, apart from the GMAT, your profile seems very competitive. Let me lay out the strengths:
worked in Africa? check
worked in the Middle East? check
worked in "volatile" regions? check
worked in the Peace Corps (HBS and Stanford love this, btw!)? check
worked in international global-level diplomacy/similar stuff? check
decent GPA that doesn't need explaining? check
Of course, I know nothing about your age, ethnicity, nationality, background, but based on what I see, you're competitive at schools ABOVE the range you're shooting for - I've seen people with profiles like this at HBS and Stanford, for Christ's sake!
Other than the GMAT part. I'd strongly recommend retaking it to push it above a 680ish score somehow (maybe even 700+), and reapplying next year. Don't sell yourself short in your hurry to get to bschool. Candidates who comes from international policy/diplomacy backgrounds are often a little older, so a year won't make too much of a difference.