I was not suggesting a ride from Santa Barbara to the OP. Only that it was my plan and he might be able to do something like it. One way trips are kind of fun because you really get to go some place. The I5 route through pendleton is short. For me it is such a novelty to ride on a freeway it is worth it
Yes Santa Barbara to LA in one day is hard and way-hard-impossible with a late start. The plan is to take two days with a very easy first day, stop at motel for 8+ hours sleep then depart at daylight.
Bike paths make for easy rides but at least up here, if my goal is to cover distance then many times I have to mostly avoid the bike paths because they are so slow. I'm learning where the street is faster and where the path is faster. It varies