I'm looking for suggestions for a West Coast US driving itinerary from you seasoned travellers out there. Ideally something around 2 weeks long (July/Aug), which will take us to see some of the best sights, but avoid tiring us out with excessive driving times. It might involve San Francisco/Los Angeles/Las Vegas/Grand Canyon, but you may also have some other ideas. It's our 25th wedding anniversary year so that we're looking for something really special!

I like the Vegas Zion/Bryce, Grand Canyon Los Angeles itinerary...that could easily fill 2 weeks IMO. I think if you added SF that would be too much driving IMO.

Choose either California OR the desert Southwest...two weeks is not long enough for both. If you go to the Grand Canyon, be sure to visit the North Rim, which is cooler and less crowded. The south rim will be packed and very hot (not very romantic for an anniversary trip). Zion and Las Vegas will be very hot as well-I wouldn't go there in August.
I would choose a northern California coastal trip-SF, Point Reyes, maybe Sonoma/Napa Valleys if you like wine and good food, driving up the coast to Mendocino and then up to the Redwoods. You can make a nice loop by driving through the mountains back to I-5 and then back down to SF.

I'll put in a plug for the NW.

You could easily spend a couple weeks with an itinerary that included Seattle, Vancouver, Victoria, and the San Juans.

Or, how about scenic Oregon, including the Columbia River gorge, Crater Lake, and the spectacular Oregon coast.

July/August is a great time of year for either of these itineraries, while the desert SW might be a little toasty.

In July and Aug I would stay away from So Calif and the desert -- too hot, too crowded (and for LA too smoggy). I would fly into SF and do one of the following:

Head south along the coast and see (not necessarily in this order, map isn't in front of me right now) Monterey, Carmel, Big Sur, Hearst Castle, and anything and everything in between. You'll have stunning scenery, lots of beautiful and romantic places to stay, nice restaurants, shopping, ocean views, as well as nice places/attractions to visit if you want to do more than just enjoy each others' company -- Monterey Bay Aquarium, Hearst Castle, 17-mile drive (from Pacific Grove to Carmel), golf to name just a few. If you go to Big Sur, try Nepenthe Restaurant -- it's a local icon right on the highway (or technically right above it) that's been around for years, has good food (albeit a little pricey) and a view to die for. Also has a nice gift store with local crafts, books, new age stuff, etc.

or

Head north via Hwy 101 to 128, a scenic road that will take you to the coast and get you there about 6 miles north of Elk. Our favorite romantic getaway is there -- Greenwood Pier Inn (http://www.greenwoodpierinn.com/inn/inn.html). You can stop off there for a few days or just head north to Mendocino, Fort Bragg, and beyond. You'll have Jaw-dropping scenery once you hit the coast. You can continue up to Eureka, and even Oregon if your of a mind to. It all depends on how much you like to drive in one day, how long you like to stay in one place, and how many roses you like to stop to smell. Most of the 'attractions' up here are centered around relaxing and communing with nature. Ocean, redwood forests, botanical garden (Fort Bragg), and probably other things I've failed to mention. Just remember that once you're on the coast, driving takes longer because of the windy roads and the gorgeous scenery that everyone wants to slow down to enjoy. If you don't mind flying into one airport and leaving from another (if indeed you're flying in), you could take the full two weeks to drive up to Oregon and then fly out of Portland. It's a gorgeous drive and Oregon has lots to offer too.

Coming from the UK we found the following worked well although we had 17 nights.
San Fransisco 3 nights
Mendocino 3 nights (beautiful town)
Napa Valley 2 nights (you could miss this out unless you enjoy wine)
Lake Tahoe 3 nights - never seen blue like it
Yosemite 3 nights
Carmel 3 nights
Then back to SF Airport

I too would avoid the desert in July/August. If you must see LV or the Grand Canyon, consider flying to LV and taking one of the various one-day flying tours of the Canyon that are offered. Pricey, but the offset is that accommodation in LV in the summer can be cheap (there's a reason) whilst accommodation near the Grand Canyon, which is scarce, will be at peak prices. Add the driving time, car costs, etc., and the fly-tour option doesn't sound so unreasonable.

I too would recommend a coastal holiday instead. My pick would be a one-way tour on the coast between LA and Seattle, seeing the California coast, Redwoods, and Oregon coast as well as some of the most attractive cities the US can offer.