Don't believe everything you read on the internet. There is an In-N-Out just outside of LAX on Sepulveda Blvd which I had thought was walkable. I was discouraged after reading this thread which suggests the walk to In-N-Out from LAX is not possible during a layover. Turns out, on a decent layover (~2.5 hours), it is totally possible!
We gave it a go because I am a big fan of In-N-Out. Go to the lower-level (arrivals) and head east. Turn left on Sky Way and follow it until you hit the stairs down to S. Sepulveda Blvd. Then head North and cross once you see In-N-Out on the left. It is not he most glamorous of walks, but a great way to get out of the airport. It is about a mile each way (~22 min).