The Church of Matki Boskiej Jasnogorskiej on W.Adams Ave is for sure a polish church and for some reasons the only place you can meet a lot of Poles and hear the. On the other hand, the name of Polish National Church suprised me...because I've never heard it. I've checked Polish Consul's Website and they do not mention it, however I traced some information here
http://www.losangelesmission.com/ed/articles/1999/1099cz.htm. Not much but still something. Apparently, there was some law suit about it's property.
The first Church is indeed official polish Church. The second one - I'm not so sure.