You aren't going to find 24 hour Walmart Supercenters in the city of LA anywhere near the airport or convenient to any of the freeways. I used the store locator online to confirm. Walmart generally doesn't build Supercenters in large cities due to strong resistance from local merchants, competition issues, and security concerns. Note that there are 3 types of Walmarts - Supercenters that are open 24h and have everything, standard Walmarts that are not 24h and have very limited groceries (mostly convenience food), and Neighborhood Markets which may or may not be 24h and are just groceries. Palmdale is the first place along your route that has one. There really isn't any place to do "one stop" shopping in the city of LA and you will waste time fighting traffic and trying to find everything.
For scenery, I think I'd take Trona Wildrose.