Depends on your timeline to be honest. The shining star would be Death Valley but that would take you a solid 1/2 day to get out there assuming you didn’t land during rush hour traffic, and 1/2 day to come back. Wouldn’t be the worst idea, it would just limit your trip to only that site.
There are closer areas within 2-3 hours of LAX: Lucerne, Johnson Valley, Anza Borrego.
Another option is Rasor Rd. My family makes a yearly trip to this remote spot just outside Baker, CA. It has the typical dry desert landscape, sand dunes, Afton Canyon, and is within driving distance of the famous lava tubes along the Old Mohave Rd. as well as the famous Kelso Dunes.
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