Getting to Pittsburg by bike is easy--the D'Anza Trail cuts through Pittsburg from both the east and west. At the Railroad Avenue intersection, head north toward the delta, crossing over Highway 4 (towards the delta) and then into Old Town.
Coming from the west? Take BART to the Pittsburg/Bay Point station. Ride down the hill as you exit the station, cross Bailey and the D'Anza Trail is on the right side of the Highway 4 entrance ramp.
Still not sure? Try Google's new biking directions - enter 625 Railroad Ave, Pittsburg CA 94565