If you're going to vegas from LA, you might as well check this little gem out!
It's right off the highway, although you do have to exit a few miles before to access it. If you type in the following address, it will take you right there:
S Las Vegas Blvd
Sloan, NV 89054
It was crowded when I went on a Friday afternoon, but that doesn't stop you from enjoying the huge colorful rocks. They make for some pretty nice photos too.