Hi, we are glad to add this function for you. But on the Facebook page, we cannot find this function: only add these people to your friends who speak English. You can send the screenshot about how you did it online to us. We will take a look. If we can make it done, we will update it asap.
When you use keyword to search people, the keyword format can be like this: Andy from America probably the people it searched out will from this country where people speak English. I got this idea from other people, but you can have a try, it is just a suggestion. But the bad effect is that i cannot make sure if there is result for this kind of keyword.
Have a nice day!!!