As Sinth already said, tKelt and I do it mostly and we don't think we need more translators otherwise it would only mess up. I keep you ofc in my mind, in case if someone of us has to leave the translation team.
Why don't you check yourself? You can easily see what languages exist by opening the mod file in an unzip program and going to assets/lotr/lang, or by selecting the languages ingame and taking a look at some LOTR items.
There is no translation for original Spanish itself, but there are translations for the Argentinian and Mexican dialects of it. They would be a good reference to start a translation.