Achachairu can take extreme highs, as shown in commercial plantings in Australia, and perhaps can take an occasional frost, due to its originating from foothills of the Andes mountains. I think what will be hard for this plant is long periods in winter with 50-60F weather, and more importantly low humidity of southern California. If you can give it some protection during winter, and provide it with misters or grow it next to a pond, it should do ok.