Driving in SF and LA or using public transport - which is easier / better to get around?

Hi, I am a UK (right hand drive) driver and coming to California for a week holiday. Staying for 2 days in SF, then driving along the coastal Highway 1 from SF to LA and then 4 days in LA... Just wondering what it is like to drive in the cities - SF and LA, should I rent a car for the whole week or only for a day or two to get from SF to LA?... Thank you