When defining a right, you must show who is the subject of that right.

Anyway, when that site states "All peoples have the right to self-determination" Is there a minimum number of people to aim for 'this right'? V.g. if 259 persons in Els Hostalets de Balenya say the want 'the right to self-determination', are they a nation from then?

As to when you stop with the right of self-determination, in the case of Catalonia, from a cultural, language, and historical point of view, there's enough reasons for a referendum to be held (given the discontent of the population). There's a similar situation with Quebec, for example. As far as I know, there's nothing about New York --language, history, or culture-- that would warrant a referendum, and there's certainly no reason for you as an individual to do so (you don't even have the basic political institutions).

The so-called "right to self-determination" doesn't exist in the Spanish Constitution, nor in the International Law, nor in Comparative Law.

https://elpais.com/elpais/2014/10/10/opinion/1412946101_9911...