why go to Amarillo and not San antonio

Didn't they come from San Antonio!? I think they did (if I remember right). Warren Oates' character didn't want to turn around even though Lara Switt's character wanted too. He said they were going to continue to Colorado and go skiing. Amarillo was probably the biggest town on their way to their vacation destination. Of course after the cult members started trying to kill them they were trying desperately to get to Fisher.