I love San Diego, but my opinion is driving from San Francisco to San Diego in five days is too rushed to enjoy all the PCH has to offer. With a toddler, the Monterey Aquarium is a natural destination, and I think it's enjoyable for adults too. Santa Cruz is an enjoyable stop, a very laid-back town. The boardwalk right on the beach is fun. I've heard some mixed opinions on the Hearst Castle. I liked the tour, but some people don't think it's worth it. Not sure if a toddler would enjoy it all that much.
You'll have a great time no matter what you do. Here's an itinerary to get you started:
Saturday- SFO
Sunday-SFO
Monday- drive to Santa Cruz, stay in Santa Cruz
Tuesday-drive to Monterey: visit the Aquarium
Wednesday- Carmel and the 17 mile drive
Thursday-Enjoy the incredible drive down the Big Sur coast, stay in San Luis Obispo or Morro Bay.
Friday- Santa Barbara wine country (Solvang, Buellton, Los Olivos) or Central Coast (Paso Robles area)
Saturday- depart LA
I also asked for tips on a PCH drive awhile back. The thread, with lots of good advice, is here:
http://flyertalk.com/forum/showthrea...693&highlight=