I was going to link to a video, but seeing as that may get taken down one day, here is the text description. Hope it is detailed enough! You may want to take a couple of Max Repels to lessen the pain of going all this way.
From the main entrance, go right to area one west: centre area, then go up and over the steps you can see at the top of the screen, then up and over the second set of stairs. Then up keeping the house on your right, go left to exit this area.
In the new area, take the set of stairs ON THE LEFT, up and over as before. Then keep the 3 lakes to your left and head up. Once you are past the lakes head right, then turn up and left )again, don't got past the house) then head all the way down keeping the three lakes to the right and exit at the bottom.
In this area head down and left, enter the large building and chat to the dude who will give you Surf.