To get around San Francisco you would need to cross over from Hwy 101 to the I-580 near San Rafael and follow it down through Oakland and San Jose until it hits Hwy 101 and then follow 101 to Pismo.
Traffic can be bad on this route if you hit it during rush hour or a bad accident. Try to be at San Rafael by 10AM on a week day and you should be OK.
An alternative route is a little complex- take 101 to 37 and head west around Northern end of San Francisco/ San Pablo Bay through Sears Point. This will get you to I-80 south to I-780 south across the bridge at Benicia (may still be a toll bridge) to I-680 south to Hwy-101. This route will also have traffic during rush hour. Again try to hit Benicia around 10AM.