Yes you can in all three Sinnoh games, in Platinum it is a bit more hard to catch Ponyta since it has less chance of coming out in the wild, but yes you can
Chat with our AI personalities
Route 206 , 210 , 211 , 214 , 215
Well, where can't you find Ponyta! By Solaceon Town mainly. Hope this helped :) (If it didn't either check your pokedex in Pokemon diamond or log on to www.marriland.pokedex.com and try there) You can find a ponyta in Pokemon Diamond,but if you need a Rapidash,try Route 214 (Which is next to Veilstone city) or Route 211 near Eterna city and beside the Cycling road. Hope this works and good luck.
route 206
In Yellow Version, Ponyta is found exclusively on Route 17; its encounter rate is 24%.
In route 211, use pokerader.