Fall/winter weather in Southern California is like summer most everywhere else. Sometimes it rains in December but not often. It's likely to be sunny and in the 70's (F)....think Mediterranean climate like Italy. Or...Australia.
The Santa Monica pier is fun. They have a carousel there that is charming. And Muscle Beach is right there too. If you want to come to San Diego I can come pick you up in Los Angeles. Or, I can come meet you up there and we can hang. I don't know LA as well as here, but don't worry about drugs and crime.
There are some really beautiful places here in San Diego. People come from all over the world to be here. LA is fun...perhaps you like walking on a pier and people watching like I do. There is some of the most stunning art at the Getty museum. Or, I have an extra ticket for Disneyland and we can go visit Mickey Mouse and ride teacups with Alice and Wonderland.
You're smart and you'll be safe. Especially with me. I'm a chicken.