I mean seriously man. It's a freakin movie!!! Of course it only took them a few hours! It's not a documentary that covers every aspect of their lives and the camera doesn't cut away!! They had a budget and I would personally lose interest in a movie if it documented every minute of every hour of their voyage from Philly to New York. They're not that far from each other anyway!
Notice how they have driven at night in one point of the movie, and have stayed overnight in another part of the movie while they're on their journey. It still would take longer than two or three days to WALK there, especially to NYC, but they didn't just get there in a few hours.