Alright...Ive lived in Redondo Beach, he is the lowdown on the beaches....
Palos Verdes- Lots of cliffs, mansions, stuff like that....Good place to go for searching the tidepools for cool stuff, rocky beaches...
Torrance/Redondo Beach- Big sandy beach, lots of surfers, is the southern most tip of the bike bath. There is the Redondo Beach pier that has some restaurants and bars...Lots of Mexicans fishing for mercury infested Mackrel. Boat and Fishing tours available.
Hermosa Beach- This is the super trendy beach. Same style of beach as Redondo except it has a bunch of volleyball courts. The pier area is full of bars and restaurants. Go there on a weekend night you will see a lot of barley clothed hot chicks waiting in lines to go to bars that are jammed packed with music blasting and overpriced drinks. The Comedy and Magic club is right there too. You can find some big name comedians there. Jay Leno is a regular.
Manhattan Beach- Palos Verdes is for old rich people, Manhattan beach is for young rich people. A choice of many celebrities to live there. More upscale than Hermosa. Boutique shops, trophy wives, stuff like that.
El Segundo beaches suck, dont know too much about the Marina del Ray area beaches....its a upscale area also. Phil Jackson and Kareem live in Marina del Ray
Venice Beach- (a must) For all your freak shows go here. Guys walking on glass? check. A man with no legs breakdancing? check All that stuff. Make sure you go there in the day when all the boardwalk shops are open and the place is packed with sidewalk performers. Every blue moon shady stuff (gangs) goes on there at night but that is VERY rarely. Its just a freak show down there....Want a bong, tattoo, or piercing? Welcome to Venice...You could bike all the way from Redondo to Torrance but its a REALLY long bikeride...especially when you have to bikeride back. Oh, parking in Venice is hell and will probably have to pay to park in a lot and then walk a few blocks to the beach