I wouldn't say that all California wines are powerhouses, but you will encounter any number of rock 'em, sock 'em, high alcohol, highly extracted wines as you traverse the well over 500 wineries which populate the area you mention. This ain't France, to say the least.
There are quite a few collective tasting rooms where you can familiarize yourself with the wines of several wineries at once. You might want to include one of these per day in your agenda. They can be quite congenial and practical, although they do not have that "I've-been-to-the-winery" feel. Then you might identify a few of the big names known to you in Sweden and make a point to visit these places. Finally, you can just pick a route and do catch-as-catch-can, ducking into places which just look interesting to you. As your departure approaches, you can also check to see whether there will be any special events happening.
As Robin suggests, "budget" and "Wine Country" do not usually inhabit the same sentence. But if you'd like a step up from the Super 8, then you might try this hotel:
http://marriott.com/property/propertypage/SFOAC. It's not in a very pittoresque location, but it is only about a 10 minute drive from downtown Napa and about 20 minutes from downtown Sonoma. It's reasonably priced for the area and has free parking and all the amenities including breakfast. (I'm a traveling salesman so I sleep around, so to speak.)
When you've decided when you're coming and where you're staying, we can speak again.
