Here is some information from WABA about options for cycling classes:

http://www.waba.org/events/education.php

The women's Sunday morning rides at the Bike Lane go at a C pace, if you're up for that. It's on-road around Reston, Herndon and Oakton, and most of the route is low-traffic with only a few short stretches on busier roads (and even those don't have all that much traffic -- I've ridden this route in the middle of a weekend afternoon with no trouble). I can't make it this weekend, but might be able to join them the following weekend.