I would hope that if any Costco sold untrimmed tri tips, it'd be Santa Maria!
Costco always offers a regional meat selection, which caters to its local market. The ONLY thing I miss about Southern California is the meat selection at Costco. They always had prime grade tri tips and my favorite cut of beef, flap meat. When I escaped CA and landed in Indianapolis last year, I could only find one butcher that even knew what flap meat is. He can get it, only if I buy an entire 80lb case.