Going South to Los Angeles
Caffe Pergolesi can sometimes be a traveler's hub and a good place to find a ride. There is an MST bus connecting Monterey and Santa Cruz. Line 78 Presidio. Hard to hitch otherwise, try the onramps in downtown Santa Cruz ... DON'T go to Capitola (Crappy-Toilet) to hitch. It won't work.
If you try to go to the I-5, be aware that the I-152 and the I-5 intersection is just highways. Don't even try to wait there for a ride. It's better to start walking down South and hope to get picked up by a friendly soul coming down from Bay Area.