I only wonder how much of the playing field you'll be able to see. PDA screens aren't that big. I don't think the menu bar would fit in either, so there might be a problem giving units orders, as PDAs don't have keyboards (if you can't one separately). Moving units around shouldn't be a problem though, because Civ2 supports moving with the mouse.
And to point out one big drawback: How can the City Screen fit in on such a little screen? You could make it smaller, so you see everything, but then you probably don't see much, since everything would be so small.
It's a great idea, but Civ2 was made for screens with a resolution 640x480 and above, so I don't think a PDA port would be practical, at least not without the source-code.
And again: What is it with people and porting everything to PDAs? From most threads I've read on this subject I get the impression that people don't really think over small a PDA screen really is. You'll be able to see everything within a city's city radius, but not much more.