I have a different opinion from an above post - I stayed at the Hyatt in Huntington Beach a couple of months ago and was completely disgusted by the filthy beach there. It was awful! We went for a sunset walk and I could not believe it - dirty diapers, trash of all kinds, yuck! I was afraid to let my 5 yr old ds take off his sandals. We spent the rest of the trip at the hotel pool. Also, when we left the beach we were approached by 2 scary guys in the parking lot and I was scared. The atmosphere was not a friendly one and it was just after sunset.
I am a native Californian and grew up in the LA area. I am not a fool who thinks that everywhere is safe or clean, but I am not kidding about how shocked and bummed out I was at Huntington Beach. (The Hyatt was awesome but the beach was terrible) This was in June.
I live in San Diego and have NEVER seen one of our beaches look like that, except maybe in the evening on the Fourth of July.
I would recommend Manhattan but I love Hermosa beach. It is located between Manhattan and Redondo and a beautiful beach community.
I hope you have a fun trip and if you do go to Huntington I hope it is cleaner then when I did - I found it depressing people treated the beach and ocean that way.