The BFRs will likely be launched (and possibly manufactured) at Boca Chica, TX (south of Brownsville)
That'll probably be the main launch site for BFR launches into orbit and beyond, but the size of the Hawthorne facility's big door was apparently a consideration when the latest spec was dreamed up. BFR launches from 39A might be preferred for romantic or historical considerations, but it doesn't look likely, at least not at first, and assuming the BFR ever flies.