Friday afternoons into the city are not that bad. Definitely not in the same category as Sunday traffic. The Lincoln and Holland tend to get backed up after 6 p.m., though, so try to make it there early.
2.5 hours should be plenty of time. I have been back and forth to Philly at that time of day, and it was never more than 2.5 hours. Bear in mind that I drive in the left lane all the time for a reason. YMMV.