I am from a black Caribbean background. In our culture, polyamory exists, sort of, in a DADT sort of capacity. It wasn't uncommon for a man to have several Mistresses that his wife knew of. Did she consent? Well, she didn't leave him, but that is probably due to cultural and religious expectations, the high incidence of domestic violence and lack of opportunities for women generally. The key thing that invalidates it from being "poly" in my book is that if, given the choice, she would have preferred to be in a monogamous relationship. Not every women, perhaps, but I'd say a lot would have because of their religious beliefs. And that's another reason why people probably wouldn't have been "out" even if they had the choice, the men I mean, because of the religious influence.
Overall, that's why I think there will be less ethnic minorities who would ID as poly even if they basically live a polyamorous lifestyle, simply because it isn't supported by religious scripture and therefore the communities that they belong to. This obviously assumes that someone from an ethnic minority is more influenced by religion than their Western Caucasian counterparts. Yes, North America especially has very religious groups of Caucasians, but even those groups do not practice polyandry, it's always polygamy, and is always "made good" with the religious blessing of marriage. It's not just some guy with a bunch of girlfriends. It has to be made "holy".