If the rate allows...

Another thing you can do is to do a one day rental and "drop off" at the local location. Then have another reservation for the same car class for the rest of the trip (and return to SFO).

It is not as economical as picking up at a local location because of the crazy per rental SFO taxes and a 2nd per rental CA tax. However, it gives you more choice, generally a better cleaned car and protection against delayed flights (local locations tend to have shorter hours).