The easy, traditional way is that Brahmins can't eat meat.
Indians in America have often discarded that tradition. But I think about 2/3 of Indians in America are Brahmins, so you do pretty well by just assuming everyone is a Brahmin.
Indians in America have often discarded that tradition. But I think about 2/3 of Indians in America are Brahmins, so you do pretty well by just assuming everyone is a Brahmin.
Also remember that its very easy here in India to preach something in public and do the opposite in private (not being cynical here). We are a tolerant society and especially tolerant of hypocrisy.
As you probably already know, vegetarian diet is not always black and white and can become complex with rules on days of the week, specific days on lunar calendar etc.
Now tilaka etc. Slightly more likely but bear in mind (I presume you are North Indian based on your spelling of janoi am I right?) in many places vegetarianism isn't an absolute norm even amongst Brahmans. Also I would presume purely as a matter of sociology vegetarianism would be one of the distinctive features least likely to go because it is something increasingly fashionable in the larger community whereas janoi etc. are not.
You should just discriminate based on something straightforward like car size or hat color