I don't think anyone at your level will see it as interference - most people there are simply trying to level up. At lvl 60 you'll get people who are farming, and who might see it as interference, though I've never had complaints.
As for a guild - in NW you have to do dungeons in order to get good gear. At low levels it is easy to get a group for a dungeon, and everybody there really wants to complete the dungeon. At lvl 60, PUGging (Pick-Up Group - in NW called queuing) can become very difficult. It took me about two weeks before I managed to enter Castle Never with a full group, and even then the group couldn't kill the second boss, as we had a really bad CW (Control Wizard).
The guild my main char is in doesn't have a forum, and is basically a vehicle to ask a few players you know if they'll join you for the dungeon. There are no requirements or obligations. I've gone up to 60 without a guild, then realized that in order to get even mediocre gear, I will have to get a more stable playing environment than PUGging.
Update on the guild: the guild creator (David / @cohenbear) says that it is not going to be exclusive SA, but that only English and Afrikaans will be allowed. Personally I would just have one of my toons in a guild with SAers in to make it easier to find groups when I'm actually online. The guild's name is Widowmakers.