Ouch...I would never use the public transportation in Baltimore myself (and I've lived here for two years). --Take a taxi from the airport to the city. It may cost more, but is cheaper than a trip to Shock Trauma with a gunshot or knife wound.
Tips for travelers to Baltimore:
The bus system almost ALWAYS runs late--sometimes the buses have been known to be an hour late.
Baltimore is NOT a SAFE city. Because it has some of the highest drug traffic, Baltimore is the second most violent city (the first being Detroit of course).
--Baltimore has over 700 assaults per day.
--Over 300 people are killed each year.
--Safe parts of Baltimore and bad sections are usually only a few blocks away from each other. Rolland Park, home of the wealthy and old-established families, is about five blocks away from the ghetto-esque Waverly. Ask locals or policemen to tell you where to avoid. (In Mount Vernan, for example, it is only safe two blocks east of Charles St and one block west of Charles St).
--Watch for the blue lights. The police department of Baltimore places flashing blue lights on top of streetlights in high-crime areas.
Other tips to White travelers:
Racial tensions are still prevalent in Baltimore today. Segregation still exists. Percentage-wise, the upper class is mostly White, and the lower-class is mostly Black. The middle class has long moved to the suburbs to escape the growing tensions.
--Do NOT look people directly in the eye.
--Stay indoors during the night. (Especially do not wander streets that you are unfamiliar with).
--Avoid Greenmount St.
--If an area has multiple blue lights, a police car every block, or feels unsafe, leave.
--Do not use the light train for transit. People get stabbed.
--If you are a male under 30 and see a group of early-teenage boys at dusk or later, keep an eye out and move to the other side of the street. (One of the gang initiations is to beat up a college student).
For more information about Baltimore, watch "The Wire", a HBO show about the drug trafficking and the locals admit it is very accurate in its portrayal.