No overpass, but there's a crosswalk at the intersection of Shawan and McCormick Roads. Unfortunately it's on the opposite side of McCormick from the hotels in question, and McCormick itself doesn't have a convenient place to cross on the north side.
Okay, that makes me feel better! Thank you. My travel agent urged me to check Google street maps when she realised that her recommendation of hotel was on the other side of such a major road. I don't mind walking out of my way if I can eventually get to a crosswalk and do it safer and legally.
Just now, I finally succeeded in getting the convention hotel to accept my room booking for the night of my arrival in Baltimore (Thursday) and the night of the Pocket authors function (Friday), but I'll have to check out the next morning and go elsewhere for the Saturday and Sunday nights. Nothing left at convention rates at all.