From Arlington to DC via metro is $3.00 during peak travel time (before 9:30 am weekdays, 3-7 pm weekdays, and after midnight weekends) and $1.85 non peak times. It is a very economical way to travel. I often will travel from DC to Arlington and back when in the area for work.
The Fairview Park Marriott in Arlington doesn't charge for parking and they will shuttle you to/from the Dunn Loring station (orange line). It's a very nice hotel and although I haven't been there for over 6 months, they gave us comp breakfast on weekends each of the many times we have stayed there before. The metro in DC is teriffic and economical and no getting stuck in traffic. Not sure if you've ever visited DC, but if not, you might think about taking the on and off bus (easy to catch it at Union station) that will get you within easy walking distance of the various attractions. And enjoy the history and sacrifice made by so many great Americans.
The Fairview Park Marriott is actually in Falls Church, Virginia. We stayed there several years ago and enjoyed our stay. There is lots to see and do in D. C. area and most of it is free.
We never rent a car in D.C. because it is so easy to use public transportation. My husband took a picture of this empty parking place because you don't see empty spaces very often.
The new (opened last April) Renaissance, Residence Inn and Courtyard in Crystal City are wonderful. While we stayed at the Renaissance, I visited the other two properties. The staff at all three are very friendly and knowledgeable. They have a shuttle that takes you to the metro or National Airport where you can also access the metro. Great location, wonderful staff. I may never stay in the city again.