was wondering if you’ve driven around your neighborhood and actually found a neighbor with an avocado tree?
if it will take a while to get soil tested and your avocado’s condition gets really worrisome, consider pulling it up and plant in a pot, then drench with distilled water, or just use household water if you have reverse osmosis.
it would be so wrong for anyone in so cal NOT to grow avocados, so maybe at a later time, and if you’re handy with grafting, there’s an avocado rootstoc from the caribbean supposedly immune to salt spray and salinity inherent to the tropical isles.
also, seeds from grocery bought avocados are generally viable, so if you eat avocados often you can try germinating the seeds and plant them directly on the ground with a darwinist approach. In the hopes that at least one will have the maritime gene, or alkali tolerance, or both. The healthiest ones would make good rootstoc, and perhaps even good eating varieties on their own. You could experiment with cali and florida grown seeds to increase chance of winning the gene lottery