Luck you! A fab part of the world to loiter in a car. And its beer & wine country (but don't drink & drive)! I've done the trip several times, always prefering the "inland" route from the Bay Area (vs the beautiful coastal route through Redwoods, Humboldt & Arcata). Yes, you are starting in Portland, so just reverse the below!
I like going up 80 toward Sacramento and at Vacaville taking 505 to connect with Highway 5 (stopping at Winters, CA for a good feed at the Putah Creek Cafe or Preserve. Depending on the time of day, Berryessa Brewing Co two miles west of Winters is a great place to sit outside on a hot day amidst the agricultural country.)
Further up 5, a nice western town in the Trinity Alps is Weaverville. Great hiking and camping. Redding, nice farmers market on the Saturday nestled on the Sacramento Rive (and Calatrava designed bridge). Dunsmuir is a good overnight stop-you can sleep in an old train car!
This is Shasta and Lassen volcano country, so if you like a good hike, take them on, or do a smaller day hike in Lassen's Bumpass hell to see boiling mud craters and geothermal activity. Further east is Lava Beds national Monument, chocka with old lave tubes and lunar territory.
While staying on 5 takes you to Ashland (Shakespeare festival country) & Medford (gateway to the Rogue River valley read: good wine, beer), I like the turn off onto highway 97 to Klamath falls. Small town, but has a brewery and plenty of hotels/motels.
From here, you can reach Crater lake but approaching it from the east. From here you can either go from 97 to 59 towards Eugene-great college town. or stay on 97 towards Bend- popular high desert outdoor town. If you stop in Madras, you MUST eat at Mi Casa. Yes, it looks dodgy, but its the real deal.
As for the Yosemite bit, head south on 5 towards Sacramento. Either stay on 5 and head to Yosemite from 120. OR, better is go to Lake Tahoe (hike parts of the Pacific crest Trail), & take highway 395 south through gorgeous high desert/hot spring country. Bodie is a great ghost town near Bridgeport; well worth seeing an old silver boom town. Approach Yosemite from the less crowded eastern entrance. Enjoy! about 2 years ago
Ah, my home country! (writing from Turkey right now...)
From Portland, I would head east to Hood River for a day, then head south from there... the Columbia River Gorge and Mt. Hood NP are spectacular--highlight; Trillium Lake, great for canoeing or taking a dip. If you go to central OR, also stop in Bend for a couple of nights. It's an outdoor lover's haven, and is home of several breweries including Deschutes craft beer. The drive to Crater Lake from there is only a couple of hours. I would strongly recommend this route over the OR coast, it will be more interesting, plus you have plenty of time to soak up the sun in the California beaches afterwards! about 2 years ago