goto potapsco bro, you'll love it. its only about 20minutes from you, a bunch of us ride every sunday. most of the guys from the shop (race pace in columbia), they all have sunday off and there are some nice downhills right off route 1 near Elkridge.
You can pick up a huge map from there, potapsco has over 170miles of trails its HUGE.
my favorite is Mckeldin area of the park. its exit 83 Marriotsville Rd off I-70. 5mi on marriotsville rd and its on your right. its $2 to get in before 5pm and the trails are sick. they have the 'family oriented' trails, to the 'this was a big mistake' trails. g'luck, shoot me a pm if you wanna meet up at the shop on sunday with us. peace.