South of the grapevine, You can take the 126 at Castaic Junction all the way to the 101 or you can take 118 (it becomes 23) to the 101.
If you are farther up - like nearer to Fraiser Park, you can the 138 to the 14 to 58 in Mojave and then on to Bakersfield. Then go a bit south to pick up the 5 again.