San Francisco is an affluent suburb of Silicon Valley located in Northern California. It's filled with tourists who haven't dressed appropriately for its inscrutable weather and wealthy people who have abandoned their self interests to live in what's known as one of the most liberal cities in United States.
It's somewhat rare to meet someone from San Francisco at Columbia, since they usually opt for other Universities in the state of California. They're very different from Angelenos, but they're equally liberal and open-minded.
San Francisco is, in many ways, like Boston. San Francisco has two prestigious Universities, like Boston, on its outskirts, and it's often overshadowed by a city to its south (Los Angeles, as Boston's overshadowed by NYC). And while those two more southerly metropoles are economically and racially diverse, San Francisco and Boston are dominated by yuppies and hipsters.