The traffic isn't a problem except when the event ends, then it's a logjam deluxe. Best to kill some time in the pits for an hour or so until it clears.
I always park in the designated area to the WEST of the track. Easy in, easy out. Cost $10, and it's about a 5 minute walk to the main gate, which is on the south side. Works great, unless there's been recent heavy rain (that area is not paved) - which there hasn't been.