My mom never waters her four citrus trees, but their roots may be reaching to adjacent lawns and flower beds that do get watered. All four are well established and bear delicious fruit. She never fertilizes them either. Their location is the San Gabriel Valley.
My own two young citrus trees were planted last fall, and I think I overwatered at first, giving them a deep watering several times a week. Some leaves and baby fruit were turning yellow and dropping off. Then we had such heavy winter rains that I stopped watering altogether, and this summer I've cautiously returned to watering once a week when it doesn't rain. Both trees look happy now (except for citrus leafminer curling up all the new growth) and they are developing fruit.
That's just my experience; I'm no expert at all.