You are about to experience some of the best scenery in the world! Plan to take your time between Monterey and Cambria. Monterey and Pacific Grove and the famous 17-Mile Drive through Pebble Beach are have lots to offer, and then things slow down a bit in the tiny village of Carmel, where you'll be happy just to stroll the streets and window shop and dine in the fine restaurants or cozy corner coffee shops.
Then you must shift to very low gear and savor the most incredible 60 miles of coastline in the state. Some sublime ways to appreciate this wonder: over a glass of wine in the bar at the Post Ranch Inn; over a hearty meal at Nepenthe; on a hike down to one of the many public beaches; from a hot tub at a roadside inn. Definitely NOT at maximum posted speed limit along the twisty roads, and definitely not at night, and preferably not at a time of day when the sun will be in your eyes. Take your time, for you'll not pass scenery like this again soon. Tickle Pink, Post Ranch, and Ventana are all super high-end inns in the heart of this beautiful land.
Once you have hit the flatlands south of Gorda, the first stop you might consider is for one of the 3 tours offered at are Hearst Castle (okay, it's touristy, but even seasoned travelers would appreciate the colossus of connoisseurship that Hearst's cottages represent). Look for the wild animal descendants of Hearst's menagerie roaming the surrounding grounds. Cambria, just to the south, offers cozy accommodations and some nice dining, but there's not much here to merit stopping more than overnight unless you're a hiker. If you're a wine taster, check out the wineries in the Paso Robles area between Highway 1 and 101.
At this point it's a toss-up whether you want to take to Highway 1 or 101 down coast to San Luis Obispo, where the roads merge. There are some charming coastal towns along the 1 that might merit some quick stop-offs, including Cayucos.
San Luis Obispo's mission and downtown show some loving care over recent years. I've enjoyed nice meals in the downtown restaurants that face the main street and have back patios under the trees facing the mission and central park.
Continue south on 101 past the sprawling suburbs of Santa Maria. The little town of Los Alamos (just a block or so long) may interest antiques-hunters on the right side of the highway. Otherwise, keep your eyes peeled for the turnoff on the left side of the highway for Highway 154 to Los Olivos. This old post road is loaded with serendipitous charms and you'll want to allow plenty of daylight time to get a little lost and meander through all the wineries and the little town of Los Olivos. Pick up a Santa Ynez Valley winery map anywhere and follow your bliss. High end lodging in Los Olivos, and more standard lodging the closer you get back to the 101 in Buellton.
You can choose to continue on 154 past Lake Cachuma (and if you do so, keep a sharp eye out for historic marker signs directing you to the Cold Springs Tavern, where you must stop for a glorious Tri Tip sandwich and libations and some good-natured roadside tavern atmosphere) and continue south until the road meets up with the 101 at the north end of Santa Barbara.
Or, you can turn left onto 246 from the 154 and continue west through Santa Ynez (hot air ballooning, more wineries, pretty valley views) and Solvant (windmills and all things Dutch) and out through Buellton to the 101. From the 101 south, it's just a long drive along the coast to Santa Barbara. (If there have been good rains, the waterfall at Nojoqui can make an interesting little stopover -- the falls are easily accessible by trail and a short hike.)
Santa Barbara has lots to offer. Best accommodations are either along the waterfront, or high up on the hillside (far off the highway) and with a view of town; avoid lodging with a State Street address (the main drag has tons of traffic at all hours). I like to stay south of town in the village of Montecito (where Oprah's west coast mansion is) and take trips into town from there. The mission is really glorious, and the wharf and shops along State Street are worth a day or two.
By now you have entered densely populated, freeway-laden Southern California. It's best to have a game plan for where you want to go, and a timeline so you don't get stuck in commuter traffic.
If you are purely taking your time and savoring the off-the-beaten-track sights, plan a side trip through Ojai on your way out of Santa Barbara. A meal or an overnight would be good in this small, tidy, upscale town.
I like the slower pace (and WAY less traffic) of Highway 126 that takes you from the 101 at Ventura to the 5 near Magic Mountain. The little oil town of Fillmore is cute, but mostly what this route offers is an alternative to the traffic you'll hit going through the San Fernando Valley on the 101 before it meets up with the 5 and 405.
Your LA destination will determine what routes and choices you make from this point on. On the 405 route you'll want to check out the J. Paul Getty Museum and its glorious hilltop views of Los Angeles (choose a clear day or a sunset to maximize this stop, and be sure to call ahead for parking reservations), Santa Monica, Malibu, Venice and all the rest. On the 5 route you might want to check out the Gene Autry Museum before you proceed into the downtown area.
Have a great trip!