As you can see by my username, I lived in L.A. (I’ve been in Northern Washington for two years now, but I lived in L.A. for 17 years.)
L.A. can be warm. It can also be cold. As the song says, ‘It never rains in sunny Southern California. It pours. Man, it pours.’ That’s reasonably accurate. You go months without rain, and then it hits around February and hangs around until as long as May. A few years ago it rained every day for a month. 
But generally there are dry days as well. Temperatures in the Winter and early Spring are cool, but seldom ‘cold’. Of course ‘cold’ is defined differently in Southern California. Winter temperatures can get down into the 40s (Fahrenheit – sorry, I don’t know the Celsius equivalent) and days can be in the 50s. I like Spring, since it’s not too cold and not too hot, and there’s the occasional rain shower. Often the rain is just drizzle, but often too it will pour down. Southern Californians don’t know how to drive in the rain, so freeways will be slower than usual. Local news programmes have ‘Storm Watch [insert year]!’ where they send a hapless reporter to Malibu or someplace to stand in the rain and talk about the houses falling into the ocean or sliding down the hillsides. (Houses fall down in the Anaheim Hills too.)
There’s also ‘June Gloom’. In June the mornings are often overcast, and the overcast can last until the afternoon. But generally the weather is sunny for most of the year.
July through September can be hot. In West L.A. it can be in the mid-to-high-80s or even into the high-90s. ‘The Valley’ (remember the song? Ohmygod!) is, in my experience, about 20° hotter. (I lived in West L.A. and flew helicopters in Van Nuys, 20 miles north in The Valley.) The summer heat is one of the things I hated about L.A. Wouldn’t mind a little of it up here right now though. 
The thing for visitors to do in SoCal is to go to Disneyland. You might find it incredibly lame, or you may enjoy it. Depends on your tastes. Last I heard it costs $50 per person to get in, plus parking. Rather expensive, I think. Queues to get on the rides can be amazingly long. Better to go on a weekday outside of Summer. And if it’s raining the waits should be shorter. I like some of the rides. Indiana Jones, Pirates Of The Caribbean and The Haunted Mansion are my favourites. Oh, and Mr. Toad’s Wild Ride is fun.
If you like amusement parks with roller coasters, then Magic Mountain is the place to go. Better thrill rides in my opinion. It will take you about an hour to get there from L.A. Take the 5 (Southern Californians call freeways ‘the [number]’ for the most part) north and you’ll start seeing signs after you get through the Newhall Pass. Knotts Berry Farm, an Old West themed park, has a couple of good roller coasters but it’s more sedate than Disneyland. It’s in Buena Park, which is close to Disneyland’s Anaheim home.
I went to the Long Beach Aquarium once. I liked it. I was fascinated by the jellies. You can also touch sharks and rays. In L.A. on Wilshire are the famous La Brea Tar Pits. Cool fossils there. Next door is a museum whose name I’ve forgotten (shame on me! :o ) that has lots of good art. The Page Museum?
Up the 405 in the Sepulveda Pass (that’s se-PUL-veh-dah – one Englishman I heard pronouced it ‘sepple-veeda’) is the Getty Museum. I haven’t been, but I’ve flown over it many times. I understand it is free, only you have to pay for parking. I think you may need a reservation.
My favourite place in L.A. is in Santa Monica: Ye Olde King’s Head pub. I love their fish’n’chips, and the bangers’n’mash are good too. After a meal and a pint you can stroll along the 3rd Street Promenade. I remember when this was just another shabby street. You can see it after it had been spruced up in Pee Wee’s Big Adventure. Since that time the street has been closed to motor vehicles and it is now reserved for pedestrians. There are usually a number of buskers there. One of my favourites is Psychic Cat. An Eastern European guy has a couple of cats that he has trained to hand you your fortune. Very cute.
If you go the other way, toward the beach (the King’s Head is on 2nd and Santa Monica Blvd, and the cliffs are just down the street) you can go to the Santa Monica Pier. There are a few carnival rides and arcades, and a vintage merry-go-round.
So you decide to pop into the King’s Head for a ‘traditional English breakfast’ and you feel the need to walk it off. Go down to the beach (as if you’re going to the pier) and start walking South. It’s a two-mile walk to Venice Beach, which is famous for its eclectic crowd. Go on a Saturday for the largest variety. Get your photo taken next to space aliens, see the guy with the mermaid sand sculpture (same sculpture every time), the rasta guy singing (bad) Jimmy Hendrix as he rollerskates along with his white-and-red target painted guitar, read about the evils of meat, get a massage or your fortune told, buy hemp products, beads, joss sticks, paintings and other trinkets… It’s a bizarre bazaar.
Hollywood is scummy. But then, I like scum! No, really. It’s a dirty place. But you can visit The Walk Of Stars to see if you can find the stars of your favourite celebrities. At night, on Sunset Blvd., there is The Cat & Fiddle pub. The food’s not as good as the King’s Head’s, but it’s a cool place to hang out. Sunset also features many venues for music and comedy. The House Of Blues is good. There’s The Troubadour, Whisky A-Go-Go, and others. Carney’s is a ‘hot dog stand’ housed in a couple of train carriages. Chili-burgers and Chili-dogs are great. I recommend it for a quick snack if you’re int he area. If you’re into burgers, there is a never-ending battle over which is better: In-N-Out or Fatburger. In my opinion Fatburger makes better burgers and their fries (skinny or fat) are way superior to In-N-Out’s.
If you feel like cooking (or microwaving) for yourself, go to Trader Joe’s. There are many locations. They have a good selection of very good food, and lots of snacks. I heartily recommend the Cocoa Almonds. I absolutely love them. I bought some last time I went to Trader Joe’s (there’s one 80 miles south of me here in Washington) and my friends made me take them away because they couldn’t stop eating them.
If you want to swim in the ocean, beware: Southern California beaches are not exactly the cleanest ones on the planet. Definitely do not swim for at least three days after a rain. Water temeratures in the summer are usually around 60°F or so. The warmest I remember were 65°F. Not bad, especially on a hot Summer’s day, but not bathwater-warm.
This post is growing rather long, so I’ll stop here for now.
) Personally, I prefer to stop in Baker at The Mad Greek for some souvlaki.
but pretty cool and only a couple hours from the Bay area.