Based on when I got this achievement, here is what I can assume:
There are 13 or 14 ramps in the first area, where you get the Robot outfit. You must jump a few of them for quest-related items, but many are completely optional. Make sure you travel down every road and look for a ramp to take you into a park, or behind the Trick or Treat homes.
This usually leads to a number of additional ramps, some times branching in two directions, so make sure to double back and take the other direction to cover every ramp. If it is your first playthrough, you should be hitting the X button on everything in sight to get candy. If you've been through the area if nothing is telling you to hit it, and there is no candy on the ground, use that to tell if you've already been through that area.
In the 3rd area, with the Carnival, I jumped off one of the red ramps that look like barn doors. I don't know if that actually counted, which is why I'm not sure if there are 13 or 14 ramps in the first area. Once you enter the corn maze and complete the last costume, you will enter one last area after fighting a guard.
Continue left, and you will reach a hard-to-see ramp. The ramp looks like a shadow, so be careful not to miss it. As I recall, the last ramp was facing left into a narrow vertical alley of the maze with a line of candy running up it. I spent most of the game with Reynold in the Robot costume to get around faster, so I hopped up and over the ramp before I realized it. The achievement unlocked as I landed.