The phenomenon of separate gender voting booths is rather South American. Bolivia uses it for sure, perhaps Mexico as well.
Bolivia probably, but as far as i know Mexico has mixed gender voting booths.
That would be appreciated. 
Ok, i got an answer for Xahar and whoever else who cares.
First i need to say that since 1968 we have, apart from the passport and driver's license, a National Identity Document (like this one from Carrio
http://3.bp.blogspot.com/_NH75XBEyeEM/RyV8yJ3fcDI/AAAAAAAAAi0/HnCBCk1FPM8/s400/Carri%C3%B3+DNI.JPG) that is used for most of the stuff where we need some type of identification (buying a house, vote, etc). And this document comes with a number which is your identity number and it's one of a kind, there are no duplicates and it includes both women and men.
But before 1968 we also had identity numbers and a document but it was a different document for women and for men. The guy who invented this probably never considered that women would be allowed to vote, or buy a house or something, because it was usual that a man and a woman would have the same friggin number.
So, when women suffrage became a law, the best idea Peron had was dividing the voting booth into women-only and men-only to avoid duplication or mixing the numbers or something.
Of course after the unified document this problem was pretty much solved (except for the people who had the old document) but this law was kept intact for more than 40 years and counting.
Why did they leave it like this? Well, maybe it was because a lot of people who have the old document still don't die
But I'm inclined to say that it is because basically no one thinks this is an issue, and nobody gives a crap wether the law changes or stays the same. Having lazy politicians also helps.
Hope my post isn't confusing, i usually write pretty messy when i have to make a long post
