Yes, we can successfully produce citrus in Jacksonville, Florida. As a matter of fact, Mandarin got its name from the Mandarin oranges that were grown here. While we do have to take precautions during a hard freeze where temperatures drop below 28 for 4 or more hours (I use heat lamps), most winters I have been able to harvest my crops with little difficulty. And you will be AMAZED at how much fruit one little tree will produce!
Here is a picture of my Meyer lemon tree:
I keep the height of my trees about the same height as I am, and have 5 trees along one side of my back yard – a Meyer lemon, key lime, tangerine, an orange, and a Ruby Red grapefruit. They are ripe and ready between the months of December through March.