Beta-tester, that's a possibility - being a computer engineer in industry myself, I know how to do that perfectly. The major problem, for me, is that I don't speak a word of Spanish - excepted something used for international diplomacy that starts with "filho de ....", but I'm quite sure that it won't be useful here - and therefore it's simply awfully annoying for me to search the source code to find the involved lines, because it's coded in Spanish and not in English. It could be done if the main language was English - and Spanish being the translation.
But grammar editor? Dude, I'm French... You'll get a bunch of gallicisms, and way too much "s" and "ed" added (or removed) where they shouldn't (or should) be...

You don't want that. You need a native speaker, if possible a highly educated one, to properly proofreading a text, even for a lewd game.
Prepare a French translation, then I can do it, but I won't be a good choice for any other language.