It's just LA to be honest.

Busy everywhere but also downtown is full of empty buildings and you still need to commute from Glendale even if you're an LA detective running down replicants.

Ads are talking up off world colonies in Texas.

No traffic though, so that's where it's fiction.

Really though the entire fiction relies on the contrast of inventing slaves in giant, monstrous firms while still having plenty of forgotten underclass, huddling in the lower ruins. Deckard is middle class, commuting from his empty suburb to prop up the system.