Does the PAL version of FFX work in USA PS2? What about the INTERNATIONAL version?

Is the PAL version in English?

I beleive so, as this is the version I own, and I am only answering the PAL question, the english version is indeed PAL.

No, PS2's are region-locked so NTSC PS2s can only play NTSC games etc.

If you want to play the PAL version, you'll either have to buy a PAL PS2, add a mod chip to your NTSC PS2 or use swap disks.

What are swap disks?

http://en.wikipedia.org/wiki/Swap_Magic

Can't say I know the specifics on how it operates and how feasible they are to use. I have a modded console myself.

Is this the same for the playstation one?

There's a man offering to sell me a copy of final fantasy anthology, but it' casing is American, not British.

He's quite dodgy and also tryed to sell my foreign nes games and a few other things.
:-/