I suggest the OP take his bike back to the LBS and talk to the owner. Ask him why he sold you a road bike that gets dirt in the BB "all the time". Ask why you were not apprised of the fact that the bike design allows dirt to penetrate the BB in such a short time.

Given that bike typically go years before needing any maintenance of the BB, you might want to pursue getting a refund for an obviously defective design that collects foreign objects in the bearings so quickly.