I would try Willow Hybrid. It is the fastest growing willow and works great as a privacy screen, growing as much a 6 feet a year in the right conditions. This tree is the 2nd fastest tree that fast-growing-trees.com has to offer! On their website, they are $59.99 each, but if you search them up on Google, you can find them cheaper. I found, at Nature Hills Nursery (naturehills.com), you can buy a 3-4 foot Willow Hybrid for only $15.95 each, with special deals depending on how many you buy.
But remember, ALL willows root exceptionally well in moist soil or even water, as they all contain a naturally occurring rooting hormone, so you could really buy one and

You could possibly even use a tall-growing blueberry bush, as they grow fast and produce edible, well known, fruits.

Mexican sunflower will grow fast and cheap. Find someone who has it and they will be willing to give you a stick or 2.
Golden duranta with the purple flowers is another fast grower. The butterflies love it.

We use the Tithonia diversifolia - the giant ones - as a hedge and block along a 4 lane highway . The plant grows to 20 feet tall in a very short time and rewards you with gorgeous yellow flowers for a month or more in the Fall . It roots easily from cuttings . It can be kept trimmed to a smaller size .
Downside ? It dies back in the winter months and you lose your privacy . All those 20 foot long canes must be cut down and hauled away . Pain in the ....
Duranta is lovely too but also dies back in the winter .
One of our favorites for a fast growing shrub is the Florida privet -
Forestiera segregata . It is described as :

Bushy shrub or much-branched tree with multiple trunks; insignificant flowers. Fruit a black drupe that attracts wildlife. Can be used as tall hedge plant in place of ligustrum. Calcareous or sandy soils, preferably with some organic matter. Highly drought tolerant. Readily grows from seed. Can take full sun and high salt tolerance .

This can easily be started from cuttings and grows really fast and then actually levels out at about 10 feet .

This may grow too wide for your requirements . If you need something that can be sheared or trimmed then look to the Walters viburnum . The Walters might be more suitable to your needs .

You're right gatormom. I didn't check her zone and gave zone 10 info.

i'll add florida anise to the list. dense, grows in partial sun/shade, roots very easily, grows quickly, esp if given some irrigation and fertilizer... and, it's native and very attractive.

A little more info will probably be needed here. What is the soil like where you want this hedge?

If it is away from foundations and a touch acidic the blueberries (provided you get a variety appropriate to the local conditions etc) would probably be a good choice for the full sun areas. Blueberries I hear like azalea fertilizer and mulching with oak leaves.

You said you need the plants to grow fast to at least 6 feet. Well blueberries will probably take a few years to get to that point. How tall can it be? Things like the willow or poplar will get really tall but they are probably the fastest ones to reach the 6' mark. How much width can you devote to this hedge? Keep in mind that there is no perfect living fence, they all require more space than a simple privacy screen fence does and the one that grow lick mad may require lots of pruning or be short lived.

Does anyone know for certain if those hybred screen willows are really appropriate to central FL? And How evergreen are they really? I've seen some reports that they are good to zone 9 and other that say only 8. So they might be kinda short lived here.

Here is what I might do for some quick privacy while trying to save some money. Plant some tall annuals Like Giant Sunflowers in the sunny parts of this fence line to give you a little screening while you work on getting your perminant solution. Unfortunately, the sunflowers are not a long term solution so as they die out perhaps you will have something to put in their place. For the shadier areas (how shady are they?) if they are not too shady, perhaps put up a bit of garden trellis and get some vines growing on it yardlong beans for summer and start the snow peas in October or something. In the mean time you can be rooting cuttings of whatever few specimens you can get so as they start getting bigger you can plant them into the line to start taking over from the annuals.

How long of a hedge are we looking at here?

ill mannered ache - that Florida Anise is beautiful do you have one? I never seen one before
Katie

Hi, tclynx
We are talking about 200 ft of fence. About half of that is not that shady, mostly small trees around, and half is surrounded by old large trees.

I cannot plant vines on neighbour's fence because they are type of people who trim their grass with scissors, so I can only do something on my side. They are nice people, but like to "look" and are in their backyard all the time.