Why does Benito decide to move to Mexico in the story, The Last Lovely City?

Benito's despair over his wife's death, and the guilt he feels over the way he has made most of his money serves as the motivation for his decision to move to Mexico to take care of his mother and oversee his two clinics. He seems to conclude that life in San Francisco no longer has anything to offer him, so he chooses to go to the only other place to which he has any ties.