also palenque has a huge spanish population...really, from what i have seen, the english speaking community is only about 1/2 of palenque...by numbers we are a large server, but there is the language division, and that's what makes it seems tiny compared to other servers...
i ran a PuG group a while ago with all spanish speaking players...it was actually alot of fun, and i had a couple translated phrases a friend taught me on macros, as well as memorized a couple common spanish phrases...i had no idea what they were saying half the time, but since i was not tanking, i just kinda did my thing and followed along...we only wiped once due to an accidental boss pull, but other than that, the run went smoothly and was, like i said, alot of fun...
can't speak as in depth for other servers, but from what i have experienced on them, there really isn't a "bad" server to choose(except thalia T.T, and thats by no fault of the playerbase...but maybe some AU players can come here and tell me i'm wrong)...
good luck and have fun...