Get wings and a jet turbine and rock climbing will be really easy. All you have to do is postition yourself so that the first ramp is straight ahead of you. Make a mental line that goes from you to the first ramp. Now continue that line. If it hits the finish line ur good to go. Now back up as far as you can. Press L1 to make your wings go up. Now just hold boost and you'll fly up the hill and clear all the bumps and everything.

How to get the wings: Go to White Mountain. Go into a tunnel right next to the ramp up to the Ski Jump. There should be a sign that says "Next City". Go through the tunnel and go out into the ocean. There will be a big stone building with a passage in the middle. Go in the passage. A car will give wings and propellers and explain how to use them.

How to get the jet turbine: Keep on going into the ocean to Papaya Island. Go into a tunnel next to the mayor's house. Follow the road and jump the gap with water in it. Do NOT go into the tunnel on your right. Keep going and there will be a couple of houses in a clearing on the edge of a cliff. Go into the house WITHOUT a sign next to it. Do whatever the guy in there asks you to do and then he will give you the jet turbine.