December is usually a good time in South Florida to pick and eat the Dancy Tangerines. After a cool night will usually make the tangerine sweeter. Regardless of a cool spell or not, start trying the taste in early December of a few.
However, if you leave them on the tree too long.... Your tangerine may become a nice solid orange color and juiceless.
When the tree starts to grow in usually about Feb. (could be earlier or later), It will absorb the juice from the tangerine before it eventually falls from the tree and as you noticed, this is not good. It is possible any time to have a dry tangerine if it has been really really dry. Prevent this in Nov. Dec. & Jan. by occasionally watering if dry spells are long. It is possible to also have a dry tangerine if root rot orcitrus greening is present and the tree is not getting enough water even if rains are normal. Thus many possibilities for a dry tangerine. What time of the year did you try them?
Another sign of a dry tangerine is loose skin. If the tangerine has the peeling close to the skin, it has a better chance of being juicy. However, when I pick tangerines from my tree, I usually try to eat the loose skins one first as I know they will dry out quicker in drought or if growth begins. Good luck.
Oh, i forgot to say i had one tangerine yesterday that was mostly green with a hint of orange. It had sweetness to it but was still more tart than sweet. So i guess I should say start trying today if a little orange is present. Better to eat them than something else or they rot or fall off the tree later in the year...
I looked again at your picture and see a lot of oak trees. Their roots can go 3 times the diameter of the canopy when pressured from other oaks for available water and nutrients in some South Florida locations. If the trees were mine I would decrease their size and slowly replace with fruit trees or less aggressive growing trees. If the top is smaller, the roots will need less of your fruit tree area. Try cutting with a shovel near the side to your left in the picture and see if roots are in the shallow top soil within 1 foot. They will look orangish and many strands for the leading root tips. But your yard and trees look great so maybe you have much better soil and water conditions than I.