I'd avoid lower G'town/M Street and take one of the G- or D- Metrobus routes through upper G'town to the Dupont Circle Metrorail station. Take the Red Line to Union Station, then MARC north towards Baltimore. You can then transfer to the MTA light rail system at BWI Airport Station or Penn Station. Check www.wmata.com and www.mtamaryland.com for specific information regarding schedules and fares. Yeah, you can do it in about two hours, but that assumes you'd make all your connections. And right now the Federal subsidy is $230 a month, subject to annual Congressional appropriations.