CA Central Valley

Now that I see where you are starting from, if it were me I'd come down 101 through Vallejo onto 780 and then over to 680. Take 680 down to 580 and then take that over to I-5 and head south. You'll have to pay the bridge toll at the Martinez bridge and I don't know if that's more than the GG or not. I'd have to check Google maps, but taking highway 12 across seems to add a lot of miles to me.