I drove down PCH just last August.
There are a couple of ways you can go, depending on the time you want to take...
You can...
From LAX airport, get on your right as you leave the LAX horseshoe, and take Sepulveda south. Go under the runway. The big street after you go through the tunnel will be Imperial Hwy-- take Imperial Hwy west (turn right). It ends at PCH & Dockweiler Beach. Turn left (south). You'll go past the big electrohydraulic plant just off the beach -- the small cliffs on the right is where handgliding got its start (El Segundo Beach) - there is a plaque there. As you continue south, just think that this is where the Beach Boys used to hang out in their younger days, surfing those waves.
PCH will kind of go inland a couple of blocks & you really won't see too much beach when you get to Manhattan Beach. You can either go towards the beach, and continue along, or you can stay on PCH. You'll pass Hermosa & Redondo Beach, & Torrance Beach. In front of you is Palos Verdes Peninsula. You can continue on PCH, or you can drive along the hill. If the weather is clear enough, you can see Sta. Catalina Island, but if it's hazy (& it usually is), you won't see the island. Along this drive around the peninsula, is where they filmed part of Pirates of the Caribbean. There is a well known chapel here called Wayfarer's Chapel, or the Glass Chapel (Lana Turner got married here & had to be carried up the steps because her dress was so tight) that is a popular & really beautiful spot. You'll drive past Abalone Cove, where the pirates used to stash their treasure in the "olden days," and continue on towards the south end of the peninsula. You'll pass two lighthouses - Point Vicente (great whale watching spot) and Point Fermin (where really crazy people like to go hand gliding) - they say the lighthouse on Point Fermin is haunted. You'll pass a park on the right and up on the hill on the left you may catch a glimpse of the Friendship Bell that was a gift to us from Korea back in the 60's. Straight ahead you'll come to a lookout spot where you can see San Pedro & Cabrillo Beach below you (Cabrillo Beach - they filmed part of "Face Off" there and "Pirates of the Caribbean", too). In the distance you can see the Queen Mary & the dome that used to house the Spruce Goose (or the Hercules, as Howard Hughes called his huge wooden plane). Continue down the road, and you'll come to the Vincent Thomas Bridge -- a huge green bridge that goes over the Los Angeles Harbor. Ports o' Call will be to your right and the docks for Princess & Carnival Cruises (Remember the show "Love Boat" - that's where it took off). Vincent Thomas Bridge will take you to Long Beach, and you continue there, past the town, old Navy yards, and along the lonnnng beach. That is where they have the Grand Prix every year. You'll also pass Naples, Seal Beach, Huntington Beach, Newport Beach, Laguna Beach, etc., etc. It's really a beautiful drive.
If you want to cut your time a bit, you can take the freeway & go towards the ocean to pick up PCH anywhere along the way -- catch the bridge, Long Beach, Huntington Beach, etc.
When I went down, I think I got as far as south of Laguna Beach & then headed for the 405 south, but PCH really takes you pretty far.