Not if you continually use public transportation. I go all over the place in NYC, and there doesn't seem to be a way to get the directions to default to public transportation. Having driving directions and traffic wait time when I don't have a car is kind of useless.
Press the i button in the top right hand corner of the card. Select 'Transportation Mode' from the expander. Select from Driving, Public Transport, Walking, Cycling etc.
I always use public transportation in Boston and configured it to show directions as such the first day I had it last fall. It's probably more useful if you use it this way because there are usually multiple possible routes to take and it gives a very good indication of when to walk out the door.
