Take the #11 bus on Charles or the #3 on St. Paul (#3 runs more often), They both end up on Cathedral Ave which becomes Liberty St. I'm not sure of the exact stop, but the Greyhound station is at 210 W Fayette St, so you want to go past Mt. Vernon and past the Pratt Library, once you pass Baltimore Street and the Arena you've gone too far. So get off somewhere around there (looking at a map would help) and head west on Fayette about a block and a half I think. Or you could take the JHU shuttle to Mt. Vernon and walk the rest, that would be a bit of a hike but it's free, so if you don't have a lot of stuff and it's not too cold...

User suggestion #2

Shuttle to penn station, light rail to lexington market station...i think...walk

User suggestion #3

Alright, i've done this a million times. The absolute best way is to take the 3 or the 11 (i think it's the 11 though) going down st. paul (there are stops every 2 blocks or so, the closest one is near that flower shop on the side of teh street closer to campus) and take that until lafeyette street. From there it is a 5 minute walk through chinatown (really cool place to burn some time) and you're there.
If you don't want to spend the $1.35 for the bus (exact change) then take the hopkins shuttle to the Peabody institute and it's about a 10 minute walk from there, although i'm not too clear on directions.
What i usually do is research tickets online, and then go there with a friend's student advantage card. I'm white and i've borrowed the cards from puerto ricans and pakistani's. They don't even look at the name.