Oye, wwe're discussing Yoshi? Perhaps one of the few matchups I feel I know really,
really well. It's one of the few ways in which my brother tortures me into a slow, painful demise....
Seriously though, I'm glad I'm not the only one that has trouble...
I'm pretty sure Yoshi was made just to counter PT. I mean, CG and followups on Squirtle and Charizard, great arial mobility, STUPID EGGS, being able to score strong hits when below us with pretty much nothing we can do, high recovery that can be difficult to punish, heavy armor on his second jump (Meaning he basically wins all move "clashes" in the air) super armor on his smashes.... It's a pretty big pain...
Anyway, he's my count on the matchups...
Charizard: This guy's my lead. Mostly because I think he has the best chance of the three to land the first KO, and even if Charizard bites it before Yoshi, it Leaves Squirtle in a decent position to clean up. Yoshi camps Charizard HARD with the eggs, but is possible with the right timing to run under a toss and punish with Rock Smash or something. The CG on Charizard is annoying but not a huge problem. DI away from him and hammer the jump button, and you'll be able to avoid most followups. (Offstage, at least. I've never been hit by an U-Smash out of a grab release, but my Yoshi player I don't think ever tries it.)
Offstage and in the air are where Charizard is really screwed... There is nothing you can do about an U-Air other than airdodge, thanks the Yoshi's heavy armor, and it will kill you at about 100%, more or less depending on ceiling. Yoshi can also nail you with N-Air out of the dodge before you can do anything if you don't DI away or summat... Trying to get back on the ground it a pain, as Yoshi runs along faster than Charizard can manuever in the air, and can meet you with a Smash attack or something. Landing with Rock Smash does not work, so it's best to go ahead and get that idea out of your head. Offstage, I hope you really like eggs, because chances are you'll be hit by a few. I actually have found Glide to be somewhat useful (At least, moreso than usual). You'll fly faster than Yoshi can run, manuever around the eggs better if you've gained some momentum, and can auto-cancel into a jab. I wouldn't advise trying to Glide attack an airborn Yoshi, though,.
The downsides outta the way, the upsides are few but rather nice. Best of which is by playing defensively, Yoshi has a really tough time approaching and scoring a hit. Rock Smash covery most approaches from the side, such as B-Air. Yoshi's Dash grab out reaches it and doens't activate the counter frames, but a back roll is usually enough to get out of the way and punish the ending lag. U-Air and U-Smash hinder approached from above. And of course, sheild grabbing is always a good option. I'd suggest keeping Yoshi as mid-close range, so he can't just start tossing eggs at ya.
One last thing to keep in mind. Yoshi's only option out of sheild is a spotdodge, I beleive... And we all know what Charizards F-Smash does to a predicted spot Dodge.
Squirtle: This one will be much shorter, I promise. Really, there's just not a whole lot Squirtle can do here. If Yoshi's above 70% or so, I'll usually try for a D-Throw to switch, since Yoshi's CG isn't lethal until about 20-30%. If you're quick enough, sometimes at really low percents you can force a ground break (I think you have to break before you get in his mouth...). Other'n that, if you get grabbed, once you're tossed off the edge, don't try to jump until after the spike. The jump kicks in just before Yoshi hits, and is essentially wasted if once the spike connects.
Before 70% or so, it's usually best to get to the other side of the stage, switch, and eat Yoshi's smash attack of choice.
Ivysaur: Ivysaur also makes a good lead. She does the best job at racking up damage, while avoiding it herself, but thanks to Yoshi's weight and mobility, likely won't KO outside of a lucky U-Smash or F-Smash. Other than that, alot of what was said about Charizard applies here. Ivysaur has an easier time dealing with Egg camping, mostly because she's smaller and has a projectile to fire back with. She lacks a good way to punish once she get's in there, though, except maybe a Dash grab on the shield or a spotdodge to something for everything else.
In the air, there's not a whole lot Ivysaur can do. Like Charizard, Yoshi can try to hit you with an U-Air or follow you're path to the ground and hit you then. Ivy's B-Air and F-Air are a bit more helpful than charizards in the latter situation, thanks to the longer reach, but other'n that, your best bet is to just try to manage. (It's admittedly probably easier to get to the ground than I make it out to be, but I tend to get bad juggled regardless of character, so it could be me overreacting.) Off Stage, just handle it like you'd handle any other character. If Yoshi tries to egg you, go ahead and take the edge. If Yoshi attempts an edgehog, then, well...
On the plus side, barring Yoshi's grabs, Ivysaur outranges and pretty effectively punishes everything he does. Dodged Smash attacks and Dash Grabs are just asking to get bullet-seeded, and provided Yoshi doesn't DI the popup hit, he'll be taking 30% or so before he's in any danger of getting free. This adds up stupid quick. Also, the fact that Ivysaur is the only one of the three not to get CGed is a huge plus.
Then of course, there's the fact that all yoshi can do out of a sheild is spotdodge, and we all know what Ivy's U-Smash does to spotdodges.
Seriusly, I think Yoshi's lack of OoS is one of the few advantages we have over him... :/
Anyway...
TL;DR
Start Charizard, don't get egg camped or caught in the air and everything will go alright. Charizard does a good job of limiting Yoshi's approach, but get's edgeguarded pretty bad.
Use squirtle if you think you can get a free switch with D-smash. Otherwish, just let Ivy eat a smash attack.
Ivysaur's pretty good at keeping Yoshi at bay. Bullet seed really does a number on him. The lack of CG is also nice. Again, don't get caught in the air, and everything should be alright.
