I am only considering the 5 accredited part time schools in DC/NoVA. GMU is my first choice, because I don't plan on leaving the area soon (if ever), and while GW and GULC are higher ranked, in my case I don't think they're worth $60,000 more. Not that I've been accepted at any of the Georges yet - I've only heard back from GMU, and I'm on their waitlist. I have been accepted at American and Catholic.
Among the four schools that aren't GMU (and would therefore cost ~$100k), if accepted at any/all but not at GMU, I would chose in order of the USNEWS rankings.
YOU have to decide if the name (and cost) of GW is important to you. Where do you want to work when you graduate? How hard do you want to work? Do you want a new car when you graduate? You could graduate from GMU, buy a new BMW, and still have less debt than if you went to GW. The GW name will help get you into the BIGLAW ratrace, where you will have the opportunity to work long hours for a huge salary, most of which will go to pay off your student loans. The debt load from GMU will allow you more freedom in choosing jobs - you could work for the government at a lower salary because you won't have mondo gigantic student loan payments to make.
For me, dropping 18 ranking spots (assuming the leaked 2005 rankings are correct) to save $60,000 is a no-brainer. Now if I could only get more people to decline GMU's offer so they can send me one....