In less than a week, BMW Group’s U.S.-based car-sharing service ReachNow will hit an important milestone and start operating in Portland, its second city after launching in Seattle earlier this year. The Portland service will officially kick off Sept. 19. However, the first residents to join the service will be eligible to start test driving the service during a two-week preview drive that begins Tuesday. ReachNow will announce an expansion to at least one more…