You will take Hiway 152 from Gilroy to 99. San Luis Creek CG is a pleasant place to stop, about an hour east of Gilroy. I was there a couple weeks ago. It's quiet and there are paved trails along the water (forebay). Plenty of wildlife and fishing too. It's located across the hiway from the San Luis Dam. The CG is about 2-3 miles from the hiway. $20 for electrical
hookup. The toilets are pits and you would have to drive to the other CG for a shower. The visitor center is interesting too, mostly about the CA water projects. I've never camped at Gilroy. Casa de Fruita also has an RV Park with electric and cable TV, but it's kind of a tourist trap. It's between Gilroy and San Luis Dam.