Yoshi Falls (DS) is an easy track, since its short. The only hard part about the track is cutting through the waterfalls, which can push you off the course. There are some boosters at the end of the lap, but there is a shortcut to the left of the track to cut across from other racers. The normal staff ghost's time is 1:45. It's already unlocked by default.
Centered around a steep drop into a lake with a huge Yoshi Egg in it, Yoshi Falls is sort of shaped circularly. Three points, about evenly spaced around, are flowing waterfalls that flood into the center lake. Usually, players are expected to go along the bridges under the huts to avoid slipping down into the sheer drop. Still, some risky players like to speed through the waterfalls and cut a little time off there lap, which is OK. The first waterfall is decently easy to pass, with some good Drifting making it profitable. Unfortunately, the second waterfall is a lot longer, and although it can still be passed (which is pretty hard), it will slow down your time, unless you use a Mushroom or some speed boost Item. Luckily, the third waterfall is extremely easy to pass, and its even got some Item Boxes flowing down it, which is a jackpot. Other waterfalls don't offer them, usually you have to go through the huts to get somethin'. After this water fall, there's a few Boost Pads, and then the finish line. Once again, it's pretty short.