In French if you don’t speak a langauge very well, you are said to speak it “like a Spanish cow”, or “comme une vache espagnole” [source]. For example:

• Il parle anglais comme une vache espagnole
  He speaks English like a Spanish cow
• Elle parle français comme une vache espagnole
  She speaks French like a Spanish cow

This expression was first used in writing in the 17th century, and possibly referred to vasces, that is Gascons or Basques, rather than vaches, or cows. At the time, Basque people from Spain probably didn’t speak French very well. Or it might come from basse (servant, maid), or from the use of comme une vache as an insult. Also, calling people and things espagnole (Spanish) was also an insult at the time [source].

In English you might say that someone speaks broken English or bad English, or that they butcher or murder English. Although, as the American author H. Jackson Brown Jr. says “Never make fun of someone who speaks broken English. It means they know another language” [source].

You could make up other ways to say you speak a language badly:

• I speak Russian like a Pavlovian pig
• I speak Czech like a Bohemian badger
• I speak Romanian like a Ruritanian rabbit

Are there idioms in other languages to refer to people speaking them badly, or indeed well?

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