I rode Vegas to LA a while ago and have driven the distance several times since and the route I took is still open. Providing you do not mind riding on the Interstate shoulder. I posted the route on Bikely.com . From the LA direction Take Route 66 or any way you want to the base of Cajon Pass, up the Pass on the I-15 shoulder, Just past the top exit and take the frontage road down through Hesperia to the old highway. Heading West then North then East the old road takes you to Barstow. Get to the north side of town and follow the I-15 frontage road until the signs on the ramps stop saying No Bikes. (Have lots of water in any season) Exit I-15 as you get to Baker and check out the Mad Greek's. Get back on I-15 in Baker. After you cross into Nevada exit at Jean and take the east side frontage road on into Vegas.