Since this is getting some traction:
The movie itself gives really good examples of how to write native spanish speakers.
Miguel O'hara says things like "No puedo más, no puedo más". That is a full phrase, and is his way to express a strong emotion like frustration, so it makes sense for him to want to say it in his native lenguge, because he can express it better than in english.
Is the most fool proof place to put injunctions, when the emotions are high and the character needs to express something.
Another good one is when he says: "¡Ay coño!" Those are just two words, but they are still a full phrase, because is an expression, an expresion is a full phrase in and on itself.
Also when he says "Qué maravilla..." sarcastically at Miles. That is a full phrase.
A good way to remember what is and isn't a full phase is check if it conveys an entire idea or not. Even if is just one word like "Chale", is expressing a single full idea, is like saying "Damn".
You can see how not to use it with Miles, you can tell he tries to say full phrases in spanish, but is more difficult for him because mid-sentence he forgets the words, so he just finishes the sentence in english.
"Tranquila mami, eso no es my fault."
He tries to convey: "Easy mom, that is not my fault", in spanish that would be: "Tranquila mami, eso no es mi culpa."
That is a full idea, but he just can't finish it, so the part he says in spanish is just half the idea:
"Tranquila mami, eso no es..." (Easy mom that is not...)
And is incorrect. Her mom actually gets angry because of that, and aks if he is learning spanglish, because nobody who knows spanish actually talks like that.
But Miles does that because he is not a fully native spanish speaker and doesn't fully know how to speak it.
Spanish speakers are more likely to speak like Miguel O'hara or Miles's mom. With full phrases that express single full ideas.
Keep in mind, when bilingual people speak one lenguge and then another, we have to make like a brain switch, for the most experinced is an easy one, but still a switch and it would be a mess to try and switch while you are in the middle of expressing an idea.
And since I'm perfectly aware of the nature of most of these fics, some other things to evoid mistakes.
In terms of enderment I would stick to the most easy and common ones:
Amor, with variants such as mi amor and amor mío.
And don't forget, these terms STILL need to be inside a full spanish phrase to not sound so weird. Think of them as the subject in the sentence, beacause that is what it is, is not a full idea. And as we already stabished, use full ideas only.
If not, just use english terms, is fine.
