How are Dick and Perry planning to return to the United States? What does their plan reveal about their state of mind following the Clutter murders?

They plan to return to the United States by bus. Dick borrowed money from one of his two fiances (the banker's widow) and purchased them tickets to Barstow, California. They decided to leave because they had no money, and Dick lost it because he couldn't find a job. Perry only decided to go with him because of what I believe was a sense of mistrust. Either way, neither one of them is thinking very clearly. It's almost as if they feel themselves to be immortal, hubristic.