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The bad news here is that 3 days just isn't a lot of time for this trip. Sticking completely to the freeway (I-5), without detours, this is a good 2 and a half day drive. Traffic is likely to be a significant factor as you get to Southern California, as you have to drive through the greater LA area no matter which way you go. You also could potentially see delays crossing the border, near Seattle, and possibly in Northern California, depending upon the time of day.

Going over to the coast really isn't an option. Driving the coast all the way from Washington would take you 5 days to a week, minimum. Even cutting over to US-101 for a small part of the coast would likely take up more time than you really have available. At best, you would have time to drive some of that highway, but you wouldn't have time to stop and actually enjoy the views.

When will this trip take place? There are some places you might be able to detour inland, perhaps Crater Lake, Lassen National Park, maybe Yosemite or Sequoia, although you listed this as a "fall and winter" trip, and some areas may not be accessible depending upon when you are traveling.

Since you are going to be in SD for a full month, any chance you can give yourself more time for this drive? It sounds like that's what would be most important to getting the trip you want.