Definitely welcome. I just moved down to Southern California myself last year. So I am still getting use to the area.
Banks: Bank of America, Wells Fargo, Washington Mutual, are the big ones and probably the most convenient.
Supermarkets: Whole Foods, Trader Joes, Vons
Cable: Time Warner & Dish Network
Cell Phone: Cingular/AT&T, T-Mobile, Verizon, and Sprint. I am personally using Sprint and it is pretty good.
Umm. . . what else? Feel free to ask

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Welcome to California!!!