We arrived around 11am in a rental car after having a nice breakfast in pasadena. We had no problem finding parking there on the grounds. They open up a big section of the golf course for parking and tailgating. As far as leaving, no clue as we celebrated at the hornsfans tailgate long after the game was over.
Would advise against the free shuttle. Took us two hours to get on a bus. If you're in a car, at least you're moving and can listen to post-game interviews.