I think supporting overseas teams is pointless unless you have some sort of connection to them. If there's a South African playing on the team, I will support them, otherwise I really don't bother. Soccer annoys me anyway as rolling on the floor like a pansy is a widespread strategy. I generally find local soccer rather annoying but I will support the Capetonian teams like Ajax CT if by chance I am watching a game.
Then there are the two sports which reign supreme, rugby and cricket. I support all Bok teams and was also very impressed by the Blitzbokke performance this Sunday. I support the Stormers and WP. In cricket, I support the Proteas wholeheartedly even though they've hurt me so much in the past. I also support the Cobras. Unfortunately I don't get to watch as much sport as I would like, esp. cricket, because I don't have DSTV. For rugby, I generally go watch at the gym but I generally can't spare the sort of time required by a cricket game to watch it in an environment where I can't do work simultaneously.