You mentioned in another thread that you're in the DC area. Where are you riding?

I ride a road bike on wooden bridges all the time. I generally avoid gravel since it's bumpy and dusty, but I can ride over short stretches of it with no trouble.

Also, if you give us a rough idea where you live, we can recommend some good bike shops. I personally love the Bike Lane in Burke and Reston, VA. IIRC, many people have good things to say about Proteus Bikes in College Park.