I just want to say this thread is fascinating for me. Full of relevant information for my climate. Were I live (Arizona), we have heavy alkaline clay with many rocks and only 6 inches of rainfall each year (however, I have optimal rain collection systems in place). For about four months we're subject to consistent temperatures between 90 to 130 degrees-- it does not cool off at night. Aggressive winds. The most prolific volunteer trees in the area are acacia willows (large fast growing nitrogen fixing canopy trees) and Mexican fan palms, but I've seen many species do well unattended: pomegranate, eucalyptus, olive, mesquite, bougainvillea (not a tree, but reaches tree size), Indian laurel, and others.
On my own property I have acacia willows, eucalyptus, Mexican fan palms, date palms, figs, olives, pomegranates, peaches, tamarind, argan, cypress, eldarica pine, apples, and various citrus. I was on the fence about almonds and apricots-- I saw them at the nursery and passed them up. I think I'll get some now, and make a guerrilla gardening attempt with their seeds. I'll let you know how it goes.