There is nothing like being exposed to natural language in real situations to help you develop your English. If you choose to stay with a host family, you will have an opportunity to hear and to use English in real social situations every day and be exposed to examples of natural English that you will not be exposed to in the classroom setting. You will pick up expressions, slang, and idiomatic language that you will not find in any course book and learn the nuances of language that can only be learned from frequent, authentic interactions with native speakers.