I could kiss you right now!
I agree with everything Sen said here, I think Georgetown and American would be good fits based on your criteria.
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George Mason (my alma mater) is a great place. It is ridiculously diverse, and this extends beyond being ethnically diverse. Something you might be interested in is the combination of a strong liberal arts curriculum with a strong research base. Access to DC is available with Fairfax being at the end of the orange line, but the campus is decidedly suburban. Many students take advantage of the location for internships. We have a somewhat significant population of adjunct faculty that are a great internship resource. I have friends who have interned at Meet the Press and The Washington Post, which
might be of interest to you. We've experienced tremendous growth in the past few years that has lead to increasing recognition. I would I imagine it would be a safety for you despite increasing popularity.
Student life is typically a concern for students interested in Mason. Do not believe the antiquated rumor mill. It was considered a commuter school, but this has changed significantly. Mason was classified as a primarily residential campus in February, and by 2012 will be the largest residential campus in Virginia. With over 350 student organizations there is a lot to do. I obviously recommend Greek Life, but it is not the end all or be all of student life.
Please let me know if you have any questions!