Hi, I'm Brazilian and I don't speak English very well. It's nothing that prevents me from creating a game, but perhaps not speaking the language would be a problem.
We expect games with text to be made in English (though others are fine if both participants share a language, and no text is fine too!), but there aren’t any strong requirements on proficiency :) We’ve had lots of non-native English speakers participate in the past, from various backgrounds and language levels. And your English is very good!