Nope, only the user interface of the program is english or german, which should be obvious ( ) as the first selection talks about program language and not about game language in the first place.
After that initial selection, you can select the game language.
Your lack of faith is disturbing . As i had set up this whole thing, you can be sure, that you are able to change the language into spanish with the methods i mention here.
No, the fs2open.ini is in your appdata\roaming folder as mentioned. Only exception is, if you activated portable mode in your global FSO flags, which is very unlikely.
YOU ARE RIGHT! Spanish language working here!!
Sorry for my misunderstanding. With the program you point me here, and following its its steps, changing language is like a children game! Thank you very much for all your work. This mod is just incredible!