If you're looking for a meeting place or a good stop around ½ or halfway between Palmdale and Salinas, you can try North Belridge, CA, which is about 2 hours northwest of Palmdale, or about 2½ hours southeast of Salinas.
Other possible places to stop near the midpoint include Blackwells Corner, Kecks Corner, Packwood, and Annette.
About ¼ or a fourth of the way, you can stop at Arvin, CA. This is a little over 1 hour northwest of Palmdale.
About ⅓ or a third of the way, you can stop at Bakersfield, CA. This is about 1½ hours northwest of Palmdale.
About ⅔ or two thirds of the way, you can stop at Bern, CA. This is about 3 hours northwest of Palmdale, or almost 2 hours southeast of Salinas.
About ¾ or three fourths of the way, you can stop at Old Adobe, CA. This is a little over 3 hours northwest of Palmdale, or a little over 1 hour southeast of Salinas.
If you drive straight through without stopping at all, the total distance is 292 miles. The distances shown above don't include local roads to get into each town, so if you're planning a long road trip, make sure you factor in traffic and road conditions, rest stop breaks, and interesting detours along the way. If you're in a rush, you can do the trip with zero stops, and your total travel time would be around 4 hours, 31 minutes.