If coming North on 465 from the southside, you can take Rockport Road West to Raceway Road and that is the "Back" way, you can also take 10th as mentioned. The 136 to the track off of 465 is OK if you get there early! Otherwise, have a full tank of fuel as you will burn it off in the inch by inch movement!
AS stated, the west side of the track on 136 is a mess! I suggest you take the "bus" idea being offered if you can!
Anyway, anyone coming to the US Nationals should stop by the Don Schumacher's Wonder Wagon AA/FC pit and say HI!
Justin