I was briefly on Masamune once and there were quite a few English-speakers there. If you need to be on a Japanese server, choosing Elemental or Mana world groups should at least mean you can use the shared Party Finder with the English-speaking community. I prefer full Japanese so I'm on Gaia but it's a hard life for anyone who doesn't speak the language over here.

The lag playing across the world is also not that big a deal so long as you don't have other Internet connection issues. Definitely try out the US server idea; if you're not pushing for world first a high ping needn't stop you from clearing hard content. Just requires even faster reactions