I rode from the Hot Metal to West End Bridges last week. Riding through Station Square isn't difficult, but there's a lot of foot traffic. The sidewalk on West Carson is preferable to the street, but much glass. Theoretically, you could stay on that sidewalk down to the Corliss Tunnel. Chartiers St isn't wonderful, but not horrible either, though the short tunnel is (to me) a bit claustrophobic.
Best place to hop a bus in town is in front of the Hilton. From there, 26A, 26D, 33X and 100 would all get you to Sheraden.