CA is a huge state, you're going to have to be very focused. Tahoe is beautiful, but the wrong direction. Save it for another trip. Traffic is inescapable. In the major metros there is no such thing as rush hour, it's crazy all the time.
I have bicycled from SF to Santa Monica, plus I grew up in SoCal. My folks had a getaway place in SD so lots of time spent there, too. There's a book called Cycling the Pacific Coast, which I highly recommend. It's for bicyclists, which means it is sharply focused on the specific route you want to take. The recommended side trips are reasonable distances away.
Road closures are real, as
@diapasoun mentioned. Don't trust Google to be up to date. Try the Caltrans website, AAA, Waze, and open Google searches (as opposed to Google maps). You may have to do the Coast in chunks. Install Waze on your phone and get familiar with its quirky self before you go. Also, Gas Buddy is a very helpful free app. Be aware that you will most likely not have cell signal at all times, due to terrain and population density (or lack thereof), so download stuff you might need In advance.
Also, I'm kind of surprised at the lists of restaurants, given that this is the MMM Fourm. Bring a collapsible cooler or buy a cheap one here. Fill it with picnic-y stuff for maximum flexibility, especially if you want to sneak in a few hikes. Although Nepenthe (means "No sorrows", IIRC) is truly remarkable, and worth a pit stop and stroll around the grounds, if they still let you do that. Frugal hack: sometimes, if you say you want to go to the gift shop, they'll let you in free. Not full access, but sometimes a taste scratches the itch without spending a lot of time and money.
Hearst Castle is amazing and worth the price. Beautiful setting, crazy good architecture, interesting backstories, etc. Do some research in advance so you choose the best tour. It's huge, so each tour is very focused, because you can't do it all at once. Probably wise (possibly essential) to book in advance or be willing to take whatever's available. Mid-week should be less crowded. Brace yourself for high ticket prices.
Spend no more than a day in SF. It's spendy and there's so much ground to cover. It's also well north of SFO. A hotel with parking in a spot you can walk everywhere from is optimal (and expensive - got any hotel points you can use?) in the City. Heading south, Carmel and Monterey are beautiful and 17 Mile Drive is lovely (but not free). As mentioned, JFB State Beach is iconic. So is the Bixby Bridge.
I'll stop here. Be focused, post your proposed itinerary here and you'll get lots more tips.
One more word to the wise: Groupon requires tons of advance planning. Sure, there might be deals, but availability is limited. You can buy a 2-for-1 deal for something, but then find it's booked solid well past your trip date.
Bonus tip: Buying an AAA membership could pay for itself in hotel discounts and route information alone.