A city in southern California. It is located in a part of Los Angeles County called The Inland Empire which is east and slightly north from downtown Los Angeles.
It has a population of about 32,000 people. Its climate is most often sunny, as is typical in southern California. It's close enough to Los Angeles that it's not too boring: you just go out of town for fun.
The high school's rival school is Bonita High School in neighboring La Verne. Each year they have a football game to determine who can retain a smudge pot trophy as a symbol of athletic superiority.
This is also the city that Bill and Ted lived in in the Bill And Ted's Excellent Adventure movie. However, that movie lied: there is no mall in San Dimas. I know, I used to live there in the 1990s which is when that film is set.