I have found Periwinkle (vinca) to be a plant that will live almost under any condition in California. I couldn't get anything to grow in a border along my shady sidewalk and I decided to try vinca. My parents bought a house in 1946 that had a bank of vinca already there. It is in a semi shady spot and my dad never watered it the whole summer, year after year. (I own the house now and the plants are still in great condition.)
I transplanted some out here by the roots and almost none of it died. It is flourishing in the hot sun and shade. We have a well that dries up in the summer if we aren't careful and it uses little water.
We are on 22 acres of oak woodland and the many deer and gophers don't bother it.
This vinca is a volunteer in my front flower bed. I just love how cheery and hardy these plants are.