What are you looking at getting out of this?
It looks like you have a pretty good grasp on writing judging from your post, but if you want to work on your fluency in conversation, immersion would be a your option. When you immerse yourself, you are able to pick up on slang, accents, and abbreviations that you usually don't learn in a classroom. If your mom is helping you pay for expenses, I would recommend moving out west for a little while. You'll have a good time skiing and probably be able to speak more fluently than compared to taking a class.
If you are looking at taking more of a career approach to this and see yourself applying writing in a job setting, definitely take the classes. They can teach you sentence structure, grammar laws, and writing techniques that you will only gain from taking classes. These might be a little dry in content but it will come in handy if you ever need to write reports or send large emails.