You can walk to lower level from Century Blvd or Sepulveda Blvd.
You can walk to upper level from Vicksburg Ave.
The shortest walk in theory, is to get dropped off at the 232 bus stop in front of LAX on south bound Sepulveda. There is a curb cutout for the bus stop and if there is no bus there, you can probably pull in and out quickly and let someone get off.
https://www.google.com/maps/place/Se...4d-118.3964349