Certainly you will hear a non-standard English on the streets, but most people are bi-dialectal, which means that they can make the shift from the standard to the non-standard and vice versa, depending on the context. Barbadians are such friendly and helpful people that when you tell them you are learning English they do immediately attempt to make the shift. Additionally, ALL the instructors are well-qualified, highly proficient speakers of English, with an added bonus of having certification in Linguistics.