Deus is great for looking at the show bikes, a decent cup of coffee and people watching (weekends are the best). The gear is VERY pricey.
Roland Sands Designs in Los Alamitos is simply AMAZING. Jay "Rockabilly" Skwarlo runs RSD's retail shop at the headquarters; he's a super nice guy. If you ask nicely, he'll let you see all the COOL stuff in the shop: amazing race bikes, custom bikes (including a Kenny Roberts MotoGP Proton V5 powered bike), new bikes being fitted with prototype parts, exotic bikes, etc. They have a huge offering of apparel and parts. In my opinion, this is a MUST SEE place. Only open Saturdays on weekends.
Lossa Engineering/Jay LaRossa's shop in Signal Hill/Long Beach has a nice showroom with his collection and his work space is pretty amazing, too. Some retail (shirts, hats, parts). Only open Saturday. Jay just finished filming a bike build competition show last week and I don't think he's racing this weekend, so he should be in.