I understand where you are coming from, but I still do not think you can ever separate teaching language from culture. They should always be taught interactively if your students are to be truly proficient and comfortable in the target language. Naturally, they will only pick up the culture of a country when they are living there, but you still need to teach customs etc in the
ESL classroom. Knowing just the grammar and how to speak the language will not suffice once they find themselves in an English - speaking country for any length of time. Sure, they may know how to ask directions, even how to order in a restaurant or understand a doctor, but will they know which piece of cutlery to use, how to greet a woman, how to conduct themselves in social business gatherings etc etc?
When I learned French, I also learned French culture, and I can't even begin to tell you what a help that was.