My boyfriend and I just got back from our DL trip last night and spent yesterday (Sunday) at Huntington Beach.
We actually took the OCTA bus down from our hotel in Anaheim - took four buses and an hour and a half each way, but it was worth it. For prairie-based Canadians like us no trip to California would be complete without an afternoon at the beach.
It's a very quaint place. Lots of little shops on the street in the center of town across from the pier. I wish we would have had more time to shop! Very nice atmosphere when we were there - fun crowd, and we felt safe. There were plenty of restaurants across the road from the beach. I think I saw a movie theatre as well.
The beach was expansive - you could spend a long time walking it. It was fairly clean. Very photogenic. Lots of lifeguard posts but being the off season, they were unmanned. In the winter there is a lifeguard truck that makes rounds up and down the beach. There were still lots of firepits on the upper area of the beach.
There were quite a few washrooms set behind the beach - long buildings divided into many single person units with with weird stainless steel basin toilets. I wouldn't call them clean but they were certainly usable. There were also washrooms on the pier itself.
The beach volleyball courts (of which there were many, along one side of the pier) were almost completely full with swimsuit-ed players, even in January! I guess you can bring your own ball, or rent one. Looked like fun.
The water was really cold this time of year and nobody was swimming (besides my crazy boyfriend

), but the water was thick with surfers. We spent a lot of time watching them. We noticed a few shops that advertise lessons along the beach. The Huntington Beach website has a list of companies who do lessons.
We went to Ruby's on the end of the pier for lunch. We asked for a window table and enjoyed some pretty good diner burgers and fries with a nice view of the ocean.
I think it was a great day trip. I'd definitely do it again.
Good luck with your planning!