How many different trees did you try to get oranges from? If it is an abandoned grove, you may want to try a few trees more to the center. When I had Valencia Oranges prior to the Citrus Canker destruction by the State, there were sweet and sour oranges coming off my tree. I believed it was because of cross pollination as I had a Key Lime as well as a Ruby Red Grapefruit tree within 100 feet of the Valencia Orange.