You have to protect in winter. Livermore is colder in winter then the central valley I noticed. You WILL have 20's each winter. But! the good news is I have heard of heat needy tropicals just explode in growth all summer. Some things far,far, out of the normal range. Like Poinciana and Royal palms- covered in winter- though.

It used to be rare to see them in the inner bay area. Now,they are everyplace. In ground or big pots. ALL IN FULL SUN.I do notice in winter's shortest and coldest days they will yellow...but the green returns in the heat.

You might do best with a pergola they can climb..and before they get large cover the whole thing in winter. Or,potted plants that can be moved in winter. Depends on how much production you want. A couple or.. a bagful.

The link below has a series on growing dragonfruit done by a UC researcher/small farm advisor, Ramiro Lobo. We have a field of dragonfruit (pitaya) including many different varieties at the UC research station in Irvine.

How to grow dragonfruit

Thanks guys. I bought one and will pot it in a good sized pot and see where that takes me.