Ironically, if you google "is speak good english grammatically correct" there are a lot of articles debating whether it's ok, or if "speak English well" is better. This is the kind of subtlety that's hard to understand for non-native speakers.
I don't think there's anything grammatically wrong with "speak good English". The difference to me is language register.
But a good portion don't, which makes hiring take a lot longer.