There is an Orvis shop about a quarter of a mile from the LL Bean shop at Tysons, and it's a small shop that will go out of their way to help you. (Once you are off the beltway on Rt 7, just keep going past Tysons and under the Rt 123 bridge. The Orvis shop is on the right just past the brige.)

The Bean shop at Tysons used to let you take the rod right outside the door to the sidewalk and cast, but I haven't been there in about 5 years.