Can't believe there are still people playing on the US servers from South Africa. The latency to Europe not slow eneugh for you and need to add another 100 ms to it?
I do play Alliance, on Shadowsong, but I am prerry much the only South African there.
The reason there are still so many US players is because the people there have all played WoW for a while or they've joined friends.
It's not easy to walk away from a well geared 70 to reroll on EU when all your mates aren't.
TheShogun is correct, however if you are starting new I recommend EU, simply because the south african population on US realms is diminishing its a fact I keep close ties with a few guilds on US stormrage and everyday now someone drops and rolls on EU. So without a decent body of ZA players you are stuck in US timezones so you will be raiding at 2am in a US guild.
I'm on Quel'Thalas and belong to Knights Templar Guild. There are a few saffers in the guild, but majority are not. But what an awesome bunch of people.