Restaurants in Johns Hopkins Hospital area.
You're 10 minutes away from the world capital of pit beef, out on the highway at the truck stops. If you like trucker's food, as I do, this will be a rewarding experience. The stuff is legally questionable and extremely unhealthy, but what the hell, if anything goes wrong, you're close to Hopkins. If you're interested in this kind of gloppy gastronomy, I'll try to give you more specific directions. Or you can do a "pit beef" Google. The last time I went to JH, I made sure to get some. I loved it.
John Waters features pit beef in his movie, "Pecker." Here is his comment about the cuisine:
"You have a grill and you cook this horrible meat in a pit. It's not like filet mignon, believe me, these slabs of beef that you slice. In Maryland, they're really popular. They have them everywhere. I did my research and went to the biggest "real" pit-beef stand and was told that amateurs sell it on the weekends, because health inspectors work Monday to Friday."
Addendum: A fragment from a Baltimore City Paper review:
"Big Al's (7926 Pulaski Highway,  574-3030) sits beside a dance club and across from a bargain motel where the late Joseph Palczynski, I'm told, had occasion to hang out. You can eat at a picnic table under a canvas covering or in your car, as we did. We asked for a pit beef, medium rare ($3.75), and a pork barbecue ($4).
"What a revelation! The beef--rosy, moist, and fragrant--had the taste of good prime rib, and the serving was enormous, its thicker-than-usual slices still meltingly tender. The pulled pork, almost as generous, tasted perfectly sweet and sour. The juicy pork held its shape enough that we could pick it up and eat it like a sandwich. Primo pit, primo pork."
I haven't been there recently, but as recently as a year ago, the cafeteria in the School of Public Health has REALLY good hamburgers--my wife and I would go there when we had a day off.
Two other places that aren't far away. (1) Simon's on Fairmount. It's a bar, but the kitchen serves much more than bar food. (2) Good, very reasonably priced Spanish food can be found at Arizona (25 S. Broadway). Stick to the seafood, but it is a place that you can practice your Spanish if you're so inclined.
Well, I must agree with the Pit Beef comment, although i think "questionable" is a relatively mild comment.
That being said, at JHH you're fairly close to both Canton and Fells Point. I'd stay away from anything directly in the JHH area; most of the area is unsafe and the food isn't much better.
In Fells, check out the following:
John Stevens, Ltd - It's a combination of sushi, seafood, and steak, with a distinctly local atmosphere and really good food.
Dudas Tavern - Another local place, with really good food, but really slow service. In the summer/fall, they have outside tables. The food is excellent - mostly pub fare - but be prepared to wait. And by 6-7 p.m., the waitstaff is generally already inebriated.
Jimmy's - If you want breakfast diner food, this is tha place.
There are a bunch more, especially in Canton, but I'll leave those to people more knowledgeable than I.
Nearby JHH is "Henninger's" on Bond St., a very reliable, small, rowhouse restaurant. No reservations are taken, and when you walk in, you're usually confronted with a boisterous bar scene. But the dining room is sweet and romantic--the often tattooed waitresses (I mean that many of the waitresses that work there have tattoos, not that particular waitresses often but not always have tattoos --that would be weird!!) help to de-quaint the dining experience. I remember a good shrimp appetizer and perfectly agreable crab cakes.
If you're having some late nights around the hospital, try out "Blue Moon" cafe on nearby Aliceanna St, which opens for breakfast after midnight, at least a few nights a week.