If you're around BWI you'll certainly want to rent a car.
Agreed 100%
Cabs are very expensive here in Baltimore, and as Todd pointed out, you generally have to arrange for them in advance.
The funny thing about the Baltimore Washington airport is that it isn't in either. If you're staying near BWI, you're 10 miles out from Baltimore. I know that sounds like nothing, but it's a different world entirely. The area surrounding BWI is composed of tons of business parks, some hotels, and some chain restaurants.
I was born, raised, and continue to live in Baltimore; Otterbein (near Camden Yards), then different parts of Federal Hill, now Hampden. Have I had my brush-ins with crime? Yes, but it's been... over a decade since any violence was directed my way, and I was a teenager then: I didn't know anything. Basic situational awareness, MUC skills, and a sharp mind will keep you safe.
Are there war zones in Baltimore? Yes. But they're pretty easy to avoid. The night scene can be found on The Ave in Hampden, Broadway in Fells Point (don't wander away from the water past Eastern), The Square in Canton, and the general area around Cross Street / Charles Street in Federal Hill. Drunk guys at a bar are a more likely threat in these areas than thugs.
The cops here are pretty busy dealing with the thug-on-thug violence: they don't hassle decent citizens. You should definitely leave the pistol at the hotel room, but you're not going to be noticed or hassled for pocket clips or anything like that.
If you drive into Baltimore from BWI, I'd recommend getting on 295 North > 95 North > Key Highway exit. This is the 'back' way into the Federal Hill area, and from there you can hit The Inner Harbor (tourist traps), or any of the spots I mentioned before, without driving through any sketchy areas. It also tends to be less congested than the 395 option. Taking wrong turns after getting off of 395 can indeed take you to trouble spots.
What types of restaurant do you like? What types of bars? Are you looking for unique Baltimore experiences (minus the crime, of course), or just a decent place to get a bite? I'm happy to make more specific recommendations.
I'll eat just about anything but would prefer to skip the chains.
The bar scene isn't my thing, but watching the night life zoo can be amusing.
That's the bad part about coming to town for business, you are stuck looking at the cool stuff through glass because it's closed for the night.
I do have a cousin in the DC/Virginia area so I will probably be down that way visiting her, so maybe a range trip is a good possibility.
I'll be PM'ing a few of you once my plans get finalized.
Thanks
"For a moment he felt good about this. A moment or two later he felt bad about feeling good about it. Then he felt good about feeling bad about feeling good about it and, satisfied, drove on into the night."
-- Hitchhiker's Guide to the Galaxy --