For the absolute EASIEST shore dive, go to the Casino Point dive park in Catalina!
Casino Point There are always other divers there, and often this is where instructors take their beginners for their first ocean dives so on weekends you'll see a lot of classes.
You have to take the ferry there, and it can be a schlep, but it's definitely the easiest shore diving around.
If you don't want to deal with the schlep, there's lots of shore diving all over SoCal. I'm sure others with more knowledge of diving in OC and SD will answer (I'm up in Ventura County), but I'll start it off with this: shore diving is always more challenging than boat diving (getting dumped by waves is not fun when you're a newbie -actually, it's not fun EVER!). So I wouldn't say that any beach diving sites are "easy". But it sure is cheaper! Laguna Beach has some very nice shore diving with relatively easy entry points, when the conditions are good. I'm partial to Heisler Park. Just watch out for the surf - as a new diver, I would avoid going in when the waves are any higher than ankle-slappers, until you have more experience.
If your wallet can handle it, I would do your first few ocean dives either at Casino Point, or off a dive boat. There are a number of awesome dive boats in the SD area - here's a great link that tells you about ALL of the dive boats in California:
California Dive Boats : The Official Page
For shore diving, be sure to read the excellent sticky at the top of this forum:
http://www.scubaboard.com/forums/socal/263669-so-whens-best-time-dive-particular-shore-site.html
Welcome to diving!