桜便りって英語でなんて言うの？

ご質問ありがとうございます。 ”Sakura greeting from Japan” sounds a bit strange, but I think it is a good kind of strange! You should change it to, "Sakura greetings from Japan" (add "s" at the end of "greeting"). I also gave you two other sentences you can use! ご参考いただければ幸いです。