For meteor showers the statement "before dawn" is correct for virtually everyone, anywhere. The reason is simple: the Earth is rotating towards the forward motion of our orbital path and we tend to run into the most particles (meteors) at that time. Bugs on a windshield. You are right in bitching that in this case, the Perseid meteor shower is more visible for Norther Hemisphere observers. Not likely you'll see many down in Argentina.
I should note the best display of meteors is only going to happen when you are out at a dark rural location with an unobstructed horizon. Rarely do they tell you the forecast rates are for an ideal situation that few could possibly achieve. You will see less than 100 per hour but one meteor per minute is likely at peak and its pretty impressive to watch.
As to what part of the world will see it best does depend on your longitude, so it is related to your timezone. Good observation. The point of maximum meteor stream density, the peak of the meteor shower, can be narrow or wide. The Perseids are an old meteor shower seen for thousands of years and its peak is fairly broad, many hours. Therefor there is some latitude in your position.
The best source of information about meteor showers, including their predicted peak time, is going to be found on the International Meteor Organization (IMO) website. They have a "live" update running for major showers like the Perseids. Consult their yearly calendar for predicted 'peak' dates. Many yearly astronomical handbooks provide meteor shower information as well. [shameless plug] I wrote an iPhone app (Meteor Shower Guide) using IMO and American Meteor Society (AMS) data that calculates your peak time based on your phones timezone setting, and its in local time! No need to wait for someone to tell you about a meteor shower, it will add it to your iPhone's calendar if you like.
The question that always drives me crazy is when people ask "where do I look?". Just look up! If you go out to a dark site with a clear horizon you will see plenty of meteors during the Persied shower. You'd have to be asleep or looking at the ground to miss them. If its clear at your location Saturday night to Sunday morning get out and watch.