Triad Stone is totally bilingual. The language will default to the PAC region, however you can select either in the options menu, so it can be played in English or Japanese no matter what version and no matter what PAC combo you choose to use.
And if you actually have bought an LA and PAC, you would be a fool to not spend $100 on Triad Stone. Seriously, spend all that to get the setup then not spend another $100 to get one of the best games on the system? Lunacy imo. Of the 3 "anime action games" on the system: Triad Stone, Road Blaster, Time Gal... Triad Stone is the best of them by far. The most fun, the best gameplay, a must own. The other truly must buy imo is Vajra 2, but good luck getting that one these days....