J, only if they're very good. Grammar Monster is designed for people who write English well. It is not cluttered with basic grammar points which a native English speaker would already know.
For example, it would explain how to use a colon and when to use capital letters, but it would not show verb conjugations or other simple stuff which people know just by being able to speak English. (eg I am, you are, he is, we are, you are, they are).
I'm afraid Grammar Monster is designed for native English speakers. There are some great sites out there which teach the things you're after. Here is a start.