So Coast city was originally thought to be located somewhere between Northern California and Southern Oregon. Other evidence eludes to somewhere between Los Angeles and San Diego. However, currently more comic book evidence points to a city close by Edwards Air Force base. These cities could possibly be Lancaster and Palmdale located in south; California City, Mojave, North Edwards, and Boron located in the north; Rosamond located in the west; and Tehachapi located in the northwest.
I know St. Roch is New Orleans (from personal experience). I think Johns’s run at multiple times said Coast City is in Northern California.