Ok, I did not notice that the g16 was 20 feet.
But I did know that the 30 feet high cliff was a moderate DC (you're using the errated skill check table right?... should be DC 13 for our level). 13 is so hard for me (+11 and two rolls take best on climb)

I decided to go on that side, because I can see the guard and when he look outside and when he dont.... which in my mind make it easyer to know when to hide and stop moving, and when to get on the move.