Well, I've played FFXI for some time, and have been in many a Japanese party. Many Japanese players in FFXI already know (and use) English acronyms. I see a lot of:
PTをしませんか - PT wo simasen ka "Would you like to PT?"
みんなはどこですか - Minna ha doko desu ka "Where is everyone?"
That should get you to a party fine, then you have to discuss Skill Chains (SCs) and all that. You'll see the Japanese players are very organized, so they will know where to camp already and what SCs will be good against the mobs. But, they also won't tell you what SCs to use, so if you're not to sure, ask: Sumimasen ga, <Skill Chain> ga dou sureba ii darou? "Excuse me, but what SC should I use. The < > denotes the auto-translate function; try to use it as much as possible, because they sure will.
I hope this helped a bit, and if you have any more questions please feel free to ask.
-Jeff