A car isn't necessary at UCSB, especially if you live in the residence halls or Isla Vista. Many students at UCSB choose to use bicycles or the Santa Barbara MTD bus to get around. (Undergraduates get to ride the public bus for free!)
If you would like to drive a car or motorcycle in California, you will need to apply for a California driver's license (CDL). Driver's licenses are issued by the California Department of Motor Vehicles (DMV).
The driver license can also be used as a form of identification in the U.S. If you don't qualify for a driver's license, you can apply for a California Identification Card. The ID card doesn't give you the right to drive, but it can help if you want a state ID.