What kind of shoes and pedals do you currently have on your road bike?

If you just want to switch to mountain bike shoes, you might be able to use your current pedals with different shoes. I used to have SPDs on both my road and mountain bikes, and I used the same type of cleats for both pairs of shoes.

Recently I switched to Speedplay pedals on my road bike to fix problems with knee alignment. I live in NoVa, and the new pedals were recommended to me by the manager of The Bike Lane in Reston, VA. Since you're in the DC area, you might want to stop by if you're not too far from there to talk to them about pedals that would be good for your feet. I've found them to be very helpful in solving problems with bike fit.