So I was exploring the Kalimdor Village and I thought while I was there I might as well keep going around towards Tanaris and see if I could find a way into Southern Un goro or Southern Silithus. I finally found it and was suprised how easy it was.
Start in Tanaris and go to the ocean on the east and follow it down around that southern peninsula to where the X is.
Here is where you will start. The coordinates are about (22, 79). Follow the path upward.
Follow more white lines
Up and over
It is important that you follow this white line exactly to the cliff ahead.
Follow the cliff line all the way until you get to the next image. Note Southern Un 'Goro is to your right. You can explore that on a later trip if you want.
Once you get here, slow fall or just jump down here and follow the line up.
Here you will see a fairly large gap. I have only done this with rocket boots as I did not want to risk dying... I don't know if you can slowfall and mount and do it. It may be possible. Try it out. I'll try it soon and report back.
DONT LISTEN TO THE WHITE LINE! HE IS LEADING YOU INTO A TRAP!
No I'm just kidding. Follow the white line down the hill and to the left.
Around the mountain.
Up this mountain side
Make sure to follow the white line exactly or its really hard to get up the hill. (Run up the bumpy spiky things)
Up the mountain, hop down the other side.
Around the hill and alongside the cliff side.
Follow.
Now I forgot to take a picture of how to get up on this little mountain, but it shouldn't be too hard to figure out, but get up there and mount up (I did mount not rocketboots) and slow fall to the little bug circle thing then follow the white line to enter Southern Silithus.
Also there is a fun part to this. Once you are in a little ways, you will exit all General and Local Defense chats. Type /who <Player name> and the zone will say 'Unknown' . Tell your friends to shift click your name. Its kinda cool.
Enjoy! I've never seen another tutorial showing this way so I thought I'd share.