How far to Johns Hopkins Hospital? Can you walk? Is it safe?
They have a shuttle.
May I suggest The Carrollton Inn, which is the closest lodgings to JH Hospital?
I have done that (walking to Johns Hopkins Medical Campus from Admiral Fells Inn) - it's like 15-20 blocks due north on Broadway and it took me less than 20 minutes on foot. I had no problem walking there (and back) during the day, and I did not feel unsafe. However, I have been told by locals not walking after dark.
Get an answer from Admiral Fell Inn staff and past guests.