Sante, if you're still looking for a slip, try the marinas up on Rock Creek off the Patapsco. I know it's north of your range, but prices are significantly cheaper in that area. You'll have to put up with seeing the factories of Baltimore for scenery before taking that right to head for the Bay, but you'll save a bundle.
I kept a boat at White Rocks up there for a while. The owner, John, has slowly been fixing up the place over the past few 5+ years and the water is deep in the slips.
Bodkin Creek is pretty and you don't have the factory problem as much, but if you draw more than 4', I think it can be tricky, especially in the "Back Creek" tributary. It's been a while since I've poked in there, so try and get some more expert knowledge. But that creek is closer to the Magothy than Rock Creek. Probably about an hour closer as the sailboat flies.