Must on leash and sometimes before 9 am or after 5 pm.

Busy there we took uber

From what I seen, they are basically there all day. To avoid the larger crowds and to find decent parking, come in the morning

Water will still be a bit cold even in the summer months, typical of ocean temperatures.

No admission fee. It is a park, really. The only difficulty is finding parking. You might have to circle around several times to find a spot, or park a ways away and walk down to the area. Depends on the day of the week and time of day. Just be patient. :-)

Yes the lower deck to the Sea Lions is closed; however, there is still plenty of scenic views, beach areas, hiking & depending on water temperature (cuz of Sharks) and current, snorkeling & kayaking is generally available. La Jolla has tons of incredible shops, restaurants & museums too. Del Mar Beach, Solana Beach, Seaport Village in San Diego are all close by & beautiful.

We were there late October and there were many people in the water.They rent wetsuits and snorkeling gear nearby.

My family spent 2 days snorkeling the cove this July and didn't see any. We were able to swim with sea lions, which was amazing! Again, it doesn't mean they were not there, we just didn't see any.

I did not see anyplace.

PBWorldTraveler did a great job answering your questions. You can't see this is the photos , but the seals and sea lions are very smelly. Plus, they are protected from by law from harassment by people. You don't want to swim next to them!