Dear Steph,�I love English �.
I find your question slightly unusual, in that different native English speakers will possibly use different forms of the same question to convey their thoughts.
For my part, I would tend to say to you: "How do you say �cheval � in English?" (However, my question to you is more likely to be:"How do you say �horse � in French?") But, I imagine that if you are asking a French colleague for help with English, your question is appropriate.
This form is very similar to the French question: "Comment dit-on �horse � en fran�ais?" So, if you �re comfortable with that form of the sentence, use it. But, "What �s the English for �cheval � is not unnatural.
I hope that I have helped you.
Les