I'm a New Yorker.
If you're coming from Times Square, you can take the S train or the 7 train to 42nd St.- Grand Central (that's one stop away on the S, or 2 stops away on the 7). Then transfer to the uptown #6 train to 103 st. (I forget what street MSSM is on... 100th?). Either way, walk west to central park, and south a few blocks.
If you're coming from LGA airport (which is the closest airport to MSSM), take the M60 bus to 125th St. and Lexington Ave. (You will see a Pathmark supermarket at that intersection). The subway is at this intersection. Take the downtown #6 train to 103rd st.
EDIT: Haha, it's ok bandaids, there are just too many busses/trains to keep track of.