Heading south on the PCH isn't that bad. Once you get into Laguna Beach, it will get crowded because of the traffic and lack of bike lanes. But once you're pass that it will be a piece of cake.
Which way are you going once you get to Dana Point? I suggest you take Goldern Lantern to the harbor and then make a left and go through the state park. From there just stay on the bike lane til you get to San Clemente. It will get congested again, but only for a little while. Then you'll have to take the trail that goes pass the power plant and Camp Pendleton. Don't forget to carry your driver's license so that you can get on the base. Either that you will have to ride along I-5.
Riding South from San Clemente through the campground, then Camp Pendleton is one of my favorite and staple rides! Very few stoplights, decent roads, and light traffic (plus the Marines on Pendleton are considerably more polite than your average citizen-motorist.) Just be sure to bring a photo ID and wear a helmet, or the MPs won't let you pass.
Coming from Bong Leach, you don't have to ride the PCH through Laguna to get further South. I usually cut through Tustin, ROI, Lake Forest, Mission Viejo and Capistrano to get to the coast's points South.
Problem with getting through Laguna Beach is that it's hilly and depending on the time of day, you have to take the lane to get through the most crowded portions. Taking the lane on hilly streets with lots of traffic is not fun. If you want to avoid this part, you can probably hop on a bus and resume riding south of Laguna Beach.
Further south, you have the option of going through the Marine base or take the I-5. Last time I rode to La Jolla, I took the I-5 and must say I actually prefer it to the Marine base. The shoulder is Wiiiiide and no-one gave me any problems. I don't think a single driver even noticed I was there. Not sure how it is heading North on that stretch of the freeway.
If you want 60-70 going south, then you need to consider the return trip on PCH through Laguna Beach and Corona Del Mar. Getting up early is ok to avoid going but coming back is a bit of a problem.
I am from Huntington Beach and the Marathon organizers already pitched up the tents on the parking lot. That Marathon is on the same day as Super Bowl Sunday. There will be like 21,000 runners there. So don't go on Super Bowl Sunday, this Sunday.
Thanks all! Good advice. I didn't know about the marathon so you won't find me anywhere near that on Sunday!
Maybe Saturday I'll head out and hit San Clemente. Corona Del Mar usually doesn't bug me too much because it is so crowded speeds are low and I can easily take the lane and keep up with traffic. Not so sure about Laguna Beach. Maybe I'll take Crit's advice and do it all inland and pop out.