There are so many raw fish eaters here, so I figured, despite the fact that you're mostly non-Japanese (or entirely), you all probably know about fresh fish.
My mom's been buying her sashimi at Marukai in West Covina, and it sucks. Prior to that, she'd been buying at Tozai (near home, in Rosemead; often just okay) and Pacific Supermarket (far away, in Gardena; it's usually good). But, lately, it's been Marukai, and they suck.
So, we need to explore our options. Is there a fish buying resource online that we could use to plan out some buying trips? Are there stores that are known to have good raw fish at reasonable prices? Do the restaurants end up getting all the good stuff before it hits the markets?
I work in Sherman Oaks, so going west and then east again isn't entirely out of the question. Distance is not that much of an issue, because I can just take a cooler.