Try renting from local locations in the Mountain View area to avoid SFO specific charges. Try Alamo from the El Camino location between PA and MV, have gotten deals there in the past. Check on Kayak for cheap rates, then choose your location and look for coupons. There are a number of locations in Redwood City, too.

One way rentals always cost a lot more.

I'm seeing a bunch of Avis and Budget rentals from Belmont for about $70 in Oct., National for $80 from Palo Alto.

Good luck!