Segregation of Users by preselected category

Hey all.

What I'm looking to accomplish is the following and I'm not sure how to do it;

Users should be segrated based on preselected categories. For example, by language.

Imagine 3 users, User A speaks English, User B speaks French, and User C speaks English AND French.

User A signs up and selects English as his language. From this point forward he will only see blogs, videos, files, photos etc of other Users who speak English.

User B signs up and selects French as his language. From this point forward he will only see blogs, videos, files, photos etc of other Users who speak French.

User B signs up and selects English AND French as his languages. From this point forward he will see all blogs, videos, files, photos etc of other Users who speak French OR speak English.

User A is segregated from User B and B from A. But User C is not segregated from anyone.

It's not a permissions issue, it's simply a preferences issue. If User A suddenly learns French and wants to change his category to English AND French then he can do so.

I'm not sure what the best way to accomplish this would be. Any advice would be greatly appreciated.

Thank you kindly.