That would be the "front" way, were folks from San Bernadino and environs would typically take.
I'm not familiar with the area enough to know where Bear Valley Cutoff is.
There's a "back" Hwy 18. If you follow the road through town, and past Bear Mountain, you can take it there. IIRC, Bear Valley cut off is down in the valley once you get off the mountain. You can take it to Victorville, and catch I-15 that way, or the 138 and head to Palmdale.
Right, now I get it. Been studying my Hubbard Scientific raised relief and now I think I understand. (I'm up northeast of Palmdale)