I would drive to Hellertown and take the Bieber bus into the city -
Bieber Tours - Home It's an express bus and takes you to Port Authority right at Times Square. From there you can use any number of public transportation methods to get around. It's about an hour from Hellertown. It's just off of route 78, easy parking.
From Pennsburg, take 663, and make sure to take a left onto Old Bethlehem Pike right before you get to 309. Take this all the way through Coopersburg to avoid the construction. This will feed back into 309 just north of Coopersburg, go north just a few miles on 309, get on 78 East and get off at the Hellertown exit. Probably take you 40 minutes. The bus leaves at the stop behind the Wendy's but you buy your tickets at a gas station about 1/2 a mile away. Call Bieber to get the name and location, I know where it is, but forget the name.