Meowth can speak like a human, but can other Pokemon also be taught to speak?
All Pokemon in the Pokemon anime, with no exceptions, can understand human speech. Moreover, judging, for instance, from Larvitar in Hatch Me If You Can, they are able to do this immediately after hatching, without having to learn.
The anime generally does not focus on language problems, so as a result, there is some confusion about Pokémon language and the Ability of Pokémon to understand humans. Although it is obvious that all Pokémon can understand each other, Meowth in the episode Go West Young Meowth once mentions Meowth language, and Jessie in Who’s Flying Now? mentions Chimecho language, so it is not clear whether there is a common Pokémon language, or every species has its own.
As far as human language is concerned, Meowth in the same episode was shown learning pronunciation, not the language itself, what implies that all Pokémon have innate knowledge of human language, so they can understand human speech, and only have to learn how to pronounce its sounds, or be able to establish telepathic contacts to speak. Despite this, Misty in Whichever Way the Wind Blows once asked Meowth to translate her words to other Pokémon, and May taught her Bulbasaur the meaning of the word town in Grass Hysteria. Therefore, this ability of Pokémon is not well-defined in anime canon.