For a city that is well known for it's progressive liberalism, San Francisco sure has a lot of explaining to do when it comes to its public transportation - probably better described as "you're better off driving a crappy car with poor emission". Protecting the environment be damned.
The BART is basically the subway system that connects the different parts of the Bay Area. They charge an arm and a leg to use (NY subway rides are $2.50, and normal rides in SF cost around $5).
The Cal train is the commuter rail. They seem to be affordable for the most part but the number of trains are scarce. Today, for example, I found out at 10pm that the last Cal train left at 915pm.
And neither really gets you to your intended destination other than your office in downtown SF. Prepare another $2 for the bus ride over to your true destination.
All of this which roughly translates into "I need a car" or else it's going to cost both my money and my time. Shame on the Bay Area transit system!