If you are heading to or from LA on I-15, and you think you're going to end up staying the night in Barstow here is one suggestion:
Ask your ride to drop you off at exit 178, Lenwood Road. Walk East, as the road bends South you'll see two outlet malls, Tanger Outlet and Factory Merchants. You want to go to the further away from the interstate, Factory Merchants. You'll find that it is nearly abandoned. In the complex you will see a map of the area, a directory. Look for building number 3 on the map. Walk to the pathway between buildings number 3 and 4 (on the North/East end). Here you will find an easily scaled trellis. Climb it. Then access the roof. if you have a computer there are working electrical outlets on almost all of the air conditioning units, and wireless internet was coming from somewhere. It's a nice place to sleep when the weather is good.
Find it on Google maps: 2582 Mercantile Way # 15, Barstow, CA 92311, USA