I assume you're visiting friends/family in Lancaster (because why else would anyone go to Lancaster)? Ask them about the last leg of your trip. The Antelope Valley is laid out on a grid, but not every road goes all the way through. There are some features out there like an airport, Edwards AFB, and the El Mirage dry lake that might block your progress.
There are decent highways that aren't freeways. The 58 on the north end is a good road from Barstow to Mojave. On the southern end of the valley is the Pearblossom Highway (138?). They're both good roads and I've towed on both of them.