I am going to make a few assumptions.
800 miles from Portland to San Fran - - about 2 weeks.
So I'm thinking last week of Oct, first week of Nov.
Maybe closer to three weeks because days are getting really short.

Here are the climate normals from the Western Regional Climate Center:
https://wrcc.dri.edu/Climate/west_coop_summaries.php

Newport
Oct - 61/46; 5.4"
Nov - 55/42; 10.1"

Crescent City
Oct - 64/46; 5.2"
Nov - 58/43; 9.8"

Fort Ross
Oct - 66/47; 2.4"
Nov - 62/45; 5.2"

Until you get pretty close to San Fran, it is likely to be wet and chilly.
You might have a pleasant window, but by November it is unlikely.

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Have you considered an interior route?
Fall rains start earlier on the coast than inland.
Temperatures are cooler, but feel much colder on the coast.


Bend -
Oct - 63/32; 0.7"
Nov - 49/27; 1.5" (3.4" snow)

Asturias -
Oct - 67/28; 0.9"
Nov - 52/23; 1.4" (3.0" snow)

Yuba City
Oct - 79/50; 1.2"
Nov - 65/42; 2.4"