Zipcar provides cars that can be rented by the hour or by the day. They have two locations in San Diego – the UCSD campus, which is near La Jolla Shores, Torrey Pines, and University City and the UCSD Medical Center in Hillcrest, just a few miles north of downtown San Diego. Check for new San Diego locations on the Zipcar web site. You must apply to be a Zipcar member in advance. Learn more about Zipcar. If you are looking for Flex Car, the company was acquired by Zipcar.