We have two enormous Korean supermarkets here in DC that are fabulous, Han Au Rheum and Korean Korner. They offer a huge variety of great, hard-to-find produce and fish, super cheap, and they cover specialty items across many nationalities, including Latin American along with Thai, Chinese, Japanese, etc. They have a deli section with some fabulous – and fascinating – takeout items. Han Au Rheum even has a sit-down restaurant in it!
I’m surprised by the negative comments about Trader Joe’s’ produce – here anyway, it’s usually fine (not necessarily cheap, though, depending on what you buy). I always get 4 avocadoes for between $3.50 and $4.50, and they always ripen up perfectly.