i agree with everyone who has posted here; on the weekends the cheapest way into DC is the metrobus that goes to the Greenbelt station on the metro (the green line).

please make sure you have correct change for the bus ride. so many tourists don't realize that is this a city bus and the driver doesn't make change. you can use coins or bills. and you can pay with a $5 and $1 bill for you and your bf. when that happens i usually just mention to the driver that i'm paying for two...