For those of you headed out of town for the weekend, take note if you plan to drive out the city over the Francis Case Memorial Bridge after 9 p.m. tonight. Just got this from DDOT:The District Department of Transportation (DDOT) is scheduled to install a new overhead sign on Interstate 395, at the Francis Case Memorial Bridge, on Friday, September 19, 2008. All of the work will be conducted overnight, between 9pm and 4am,…