If you're coming up the 99 from SoCal, you can get off the 99 at
Lerdo hwy. There is a chevron gas station there and a little Mexican restaurant, go past them a very short ways, and hang a left on Zerker road.
Google Maps
This is more scenic (you go thru the orchards and groves) than 99. You will t-bone Famoso road and hang a right. The track is up the road just a bit, there a 3 entrances:
The 1st one you will come across is for racers/participants, and the other 2 for spectators.
This is the main ticket entrance in the middle:
100 or so feet to the left, will probably be another entrance/ticket booth.
re: Panama lane exit. There is cheap gas at the am/pm to the right.