How useful is Azerbaijani language in Iran?

I am planning to visit Iran soon and, unfortunately, I don't speak a word of Persian. As an Azerbaijani, I am curious whether I should try to speak to people there Azerbaijani or English, given the fact that according to different numbers, 16-25% of Iran's population comprise of Azerbaijanis.

I am aware of the fact that people in Iran understand English, but I don't want to look like a tourist from another world, would be more pleasant to feel like a neighbor there.

Speaking of my destinations, I would love to visit Tehran, Isfahan, Shiraz, Bam and the northern regions of Iran where most of the Azerbaijanis live, like Tabriz, Ardabil, Khoy etc.

So, my questions are:

how useful Azerbaijani language will be in my destinations?
would it be arrogant/unpleasing in any manner to try to speak to people there in Azerbaijani?

A local's insight would be extremely interesting!

Best Answer

I'd go with English when talking to people in public, because first of all you can never know who is going to understand you if you start speaking Azerbaijani and secondly, it would be of no special advantage to you if people knew you are a neighbor. If you happen to visit a supermarket in Tehran though (I'm not sure about other cities), you can speak Azerbaijani to its owner because almost 99% of supermarkets are owned by people from Azerbaijan there. If you really want to speak Azerbaijani to someone, first ask them "Do you know Turki?", and if the answer was Yes (which I guess is in maybe 25% of the time), then go with it.