Bitcointalk is honestly overrated in terms of learning in general. It's great for having questions and discuss/debate certain news and topics, but if you're a beginner you're better off reading articles off the web.
Do not just focus on bitcointalk because if you want to improve your English speaking and writing skills, then learn from the available resources in the internet. However, bitcointalk may be a good avenue if you want to gain more insights on cryptocurrency and its volatile market, and the worldly economic issues that are now very visible these days. Other than that, if you want to improve your English, learn from the English vocabulary first and master them.
The reason why bitcointalk is a better place for beginners to learn is that bitcointalk forum does not promote fallacy. Bitcointalk forum is highly against wrong teachings that are not real. That's why any beginning learning from bitcointalk forum is acquiring the real knowledge. Learning outside the forum like using Google is good, but in Google it is possible to come across things that are not true.