This is one thing that bothers me. The city is clearly in Tamilnadu given the store signs and Hotel sign at the end. But people are clearly not speaking tamil. Seems pretty odd.
I need to rewatch it . Can you tell me the specific time points ? My first impression of this was something like a Muslim dominated part of India given the architecture . But if it has South Indian portions then I would go Hyderabad . But if there is Tamil which I can't read so yes I could be wrong (case and point of how India is varied so even me being indian won't know things about other parts of India)
Edit : although if the militant group is operating in a different part of India than where they are from they would default to English to ease communication with the local populace . It's a quite complicated question and needs more context . Plus I think as I said it's just simpler for devs to default to English given how common it is in India and there are many plausible explanations for it such as the one I mentioned .