Seagrape is a Florida native, so that's a plus. However, it's a broad spreading tree, so you'd lose some depth in the yard. You could keep it cut low for many years, but you'd eventually lose the battle.

Bamboo - the clumping varieties - is less thick in terms of the amount of space it's going to take away from your yard. It will grow much faster than Seagrape and hide the buildings behind it. There's a lot of tree debris from bamboo, but then again, the Seagrape is going to drop huge leaves and berries. Bamboo is going to be more expensive than any other alternative.

You might also consider Areca palms. They're cheap and fast growing. They do drop fronds and berries, but the maintenance is not going to be as high with either bamboo or Seagrape.

Have you considered Oleander? Blooming in white or pink, they quickly grow tall and thick. I would layer something like variegated arboricola or night blooming jasmine in front of them. These are all very low maintenance, and forgiving of weather extremes. Give the oleander plenty of space - it will be much healthier and reduce your chances of having caterpillars if it has good circulation. Both the oleander and jasmine will bloom nicely with a good trimming 2-3 times a year.

Only problem is I HATE Oleanders. Where we lived in AZ that is all they had, oleanders, everywhere you looked, miles of them along streets and highways - Ug! but thanks for the idea.

Could you do a few different things? This way if something fails it won't be a whole wall of fail, plus it would be more interesting to have a few things to look at.

I agree that Jasmine might be a good idea for part of the planting, I can't stand to have them in my yard bc they grow so wild so fast I can't keep up with it! A grouping of bamboo clumps and Jasmine and something else would be really pretty

I have seagrapes , which I do really like but mine are kind of spindley , I think the bamboo will give a more dense coverage.

You could go with the Airca Palms. They take time to grow. So unless you can get them at a good size, it might take years. We have some but they are slow to grow. Very tall though.

The other option would be shrubs which you can let grow tall and keep clipped so they grow wide rather than up. I have a bunch in the front of my house which got so big and wide. They are great shrubs in the wrong place.

I think shrubs would grow faster than Palms. I would not suggest bamboo as they really don't provide privacy. I planted some and I now regret it. They are beautiful, but do not give us privacy. I like shrubs. They get thick enough to provide total privacy and also help with sound proofing.