I found myself in a rather interesting pickup group for Steamvaults this weekend. I found a hunter through the LFG system, and he invited a warrior, a priest, and a warlock who were his guildies. I breathed a sigh of relief -- an easy run to the Karazhan key fragment was assured. Until I noticed that I could only understand one out of every five words they said. The guild I had grouped with was largely French-speaking, and my high school French IV lessons weren't going to get me out of this one.
I explained that I didn't speak French well enough to communicate with them on Vent, and in return, they set up a macro system so that I could be informed of my role while they did the actual strategizing. Anything with an X over its head would be sapped by me, and they spoke English well enough to type out simple directions for a rogue ("left!" "resap!" "wait!") The first couple of pulls were rough, but it went smoothly after the first boss. In fact, it went better than most English-speaking groups, possibly because there wasn't annoying chatter or loot arguments.
There are many Quebecois in my guild and on my server, and from that, much of Magtheridon seems to have gained some command of French, or at least some horrible hybrid of French, English and WoWspeak. ("Vous, uh, feignez le mort?") Does your server have a lot of diversity when it comes to languages, or does everyone mostly speak one? How do you deal with multilingual guilds or instance groups?