It couldn't be easier to get to, head towards La Jolla down Torrey Pines Road, hang a right on Prospect, bear to the right and head down the Coast Blvd. Children's Pool is small cove opening to the North a little beyond Ocean Street. This may not be the most direct route. But it is the most scenic. There is usually parking available somewhere along Coast Blvd, but hey, this is La Jolla after all. After you have searched for a while you can drop your gear off at the head of the stairs leading down to Children's Pool (right next to the life guard station) and then go down the street to find parking.
There are shower and bathroom facilities at the life guard tower, half way up the stairs.
Diving is allowed in Children's Cove since the city downgraded its pollution signs to warnings, and the rope barrier across the cove was ruled illegal. Seal activists may have a line drawn in the sand, or used kelp and be holding signs asking no one to cross them. These have no legal substance. Be polite as you ignore them. Enter and exit away from the seals, and try not to spook any. Slow movements and even pausing if they look up is good. Avoid eye contact.
More information: http://www.sandiego.gov/lifeguards/beaches/pool.shtml
Even more so than most, this site should be approached with a weather eye. You should spend a little time at the top of the stairs watching the flow of the water. Traditionally the current flows down from the north and fills up the pool area, this means that you get a small rip current flowing (usually) due west out of the mouth of the Pool area. Look for the tell-tale path of small white bubbles floating out towards Hawaii.
Once you get in the water, use this rip current to float out to the several reef areas 100 to 400 feet out from the breakwater. When you come back in, try to stay south of the rip current and slip in on the westerly swell driving between the rip and the end of the breakwater. You should try to stay 10 feet away from the breakwater (more if conditions are bad) and a swell will deliver you into the cove. During your swim back into shore, take an occasional look at the mouth of the pool to ensure you haven't drifted into the rip coming out (like I tend to, I can't swim a straight line on my back with a ruler!)
This sounds like a tough entry/exit, it isn't. Advance knowledge of the water flow around the pool means you can take one of the least stressful shore dives you've ever had.
The seals of La Jolla have pretty much abandoned their perch on Seal Rock (off point La Jolla) and have taken up residency on the sands of Children's Pool. Now I like to swim with the seals, I feel a kindred spirit for an animal that is as ungainly above water as I am below. But the seals have also taken to using the pool as their own personal latrine. This had driven up the pollution levels in the pool and had caused it to be closed pretty much constantly a few years ago, though the bacteria seems to not be harmful to humans.
Out beyond the breakwater, you will find more seals, Lobster (at least until lobster season), Garibaldi, Sea Bass, and a host of other players.
Once you do get out, you will find bunches of eel grass, small flat sandy areas, and small reefs that run parallel to the shore (use these to brush up on your underwater navigation!).
Inside the pool the swells stay very small, they pick up as you proceed around the breakwater. As the current is from the north, the tendency is to drift south to the other side of the breakwater, this is not a good idea as the entry/exit area at South Casa is very small and hard to see from the water. So plan your dive to start off in a northern direction and you'll do fine.
Pretty much covered the Entry heading. Just don't swim against the rip, and don't get pushed up onto the reef, or go into the rocks just north of the pool.. When you look at the swells, judge them by their size outside of the pool. The last fatality was someone who went out on a night dive in medium to heavy swells, then got caught up on the surf facing rocks to the north of the pool. So watch your return swim.