citrusbelt--it is really pretty easy to get to Bryn Mawr from Philadelphia airport. You can take the train (I forget exactly where you switch trains, but you take the train from the airport and then change somewhere in Phila. to the one that goes to Bryn Mawr) but I rented a car at the airport and it was really easy to drive there. If you go by train, research the route online before you go so you'll know in advance where to switch.
I am directionally challenged, to say the least, so I always rent a car with GPS==it is just a bit more per day for the rental and makes things SOOOO much easier.
Here's a link that will help:
http://www.onebigcampus.com/college_profiles/bryn.htm