I'm not sure how many people actually pay attention to the language tag when they see a server, but if anyone does, saying the server is in English both isn't entirely accurate and might turn people away. For a long time we've had a strong Spanish-speaking minority if not majority at times on the server, and many of us speak both English and Spanish. If we need to translate menus and such, that's easy enough to do.
At the very least it makes it apparent to our hispanophone amigos that our server is multilingual, but at best I would hope that it increases player count. SA:MP is not dead; it's obvious looking at the non-English servers that routinely pull hundreds that it's still alive. There's no sense in not advertising that our server is multilingual when has been for years, and making that obvious could pull in new players. I do think it makes sense for the forum to remain in English, since translating is feasible.