In SoCal, TJ's is everywhere. I had one near my house, one in between my house and my office, and one by my office. This was like a 20 minute commute. It's part of culture there, like In-n-out.
I have SNAP accepting stores loaded into a gis (JOSM really) so it was quick to check. ~1/5 of the Trader Joe's stores in the country are in southern California (just a couple fewer locations than all of the northeast). More than 1/3 are in California.
