It's surrounded by vacant land - to the east to US 441, to the west to I-75, and almost unlimited area to the South. Which is why it's expected to nearly double in population within the next ten years or so:

Just in looking at aerial photos of those areas, that's not what I'd call vacant land. It's all subdivided and criss-crossed with roads. It's lightly populated with folks who may or may not be happy about that development spreading into their area. Some of those will become the folks who will complain about the congestion as the development spreads toward them.

Sure, there's lots of room to increase density, but that increased density is what will cause the problems that LA, SF, and NYC have been dealing with for decades.

very marginal ag land

Is there any ag land in FL that *isn't* marginal. ;-)

Of course, as a CA native, I'm a bit biased as to what is and isn't good ag land. Maybe as much as 1/4 of CA is some of the best ag lands in the world. That's also a part of why comparing state wide population densities between CA and FL is a bit of a fool's errand. We've got a lot of land that needs to stay agricultural. And a lot of land in the mountains that is not suitable for any kind of development beyond the most primitive of shelters.

For reference, here's that bit of "undeveloped" land to the west of The Villages:
Google: Google Maps

And here's some REAL undeveloped land in CA, just north of I-10 and east of CA-177
Google: Google Maps

--Peter