I also live in Southern California (Encino/Sherman Oaks area to be exact) and I get pretty decent LTE reception everywhere I go in So Cal unless I'm up in the mountains like Big Bear (still get signal bars there though).
I can't speak for Verizon in other areas obviously but it's pretty good out here in So Cal. All I know is that despite the unlimited data, Sprint is horrible here based on my friend's experiences so far. He has Galaxy S3 on Sprint. Rarely gets 4G signal. He lives in South Bay area.
FYI, I pay about $152, shared plan (unlimited minutes/texts, 4 GB data).