Translators between English and Spanish – and no doubt, going from English to virtually any language in the world – often find themselves wrestling with issues like this one: How do I translate Engl. ‘report’? The overwhelmingly clear choice is informe – that’s the ‘castizo’ (correct) word in Spanish. But the temptation to use Sp. reporte is great… it is certainly a recognized word in Spanish, as registered for instance by the Diccionario de la Real Academia Española, the main reference work of the institution legally entrusted with the ‘care and feeding’ of the Spanish language around the world. But it is far from universally accepted, it is clearly an importation from English, and its appearance in Spanish is quite recent (the marvelous Google Ngram tool shows it to be essentially a post-WWII phenomenon). Now, does that disqualify it as a Spanish word? Of course not; all languages are built in large measure by borrowings from other tongues.
In a case like this, we need to think carefully about the likely audience or readership, and the word’s probable impact. Is the audience largely composed of Spanish speakers in the US – who of course are the most heavily influenced by English, though far from the only ones ? Even more specifically, is the audience likely to be young? If so, there may be an argument for reporte. Otherwise, the word is probably going to sound jarring.
Other things being equal (though they aren’t always so), if the target language – i.e., the one you’re translating into – has a ‘perfectly good word’ for what you’re trying to express, you should use it (informe is a good example). On the other hand, if your likely audience/readership tends to use another word, imported or adapted from a foreign language (reporte, for instance), you should at least consider it. And if the imported/adapted word is clearly the best and most widely understood way to express something, there should be a strong presumption in its favor: input in the computing sense is moving into this category, though in the figurative sense Sp. insumo or entrada are much preferable.
The bigger picture
If you find yourself upset at the English ‘invasion’ of Spanish, it’s good to take a couple of steps back and look at the historical sweep of how languages grow and change. When a Spanish speaker drops some coins into an alcancía(money-box), stops at the airport aduana (customs) post, or complains of someone’s being mezquino (stingy) – these are all words that entered the language roughly a thousand years ago from Arabic. (For that matter, English speakers draw from Arabic with ‘algebra’, ‘chemical’, ‘divan’, and plenty of other words.) Linguists call them loan-words, oddly, though they’re never returned! English has an enormous stock of words drawn from French, a process that began in earnest with the Norman invasion of 1066 C.E. and has experienced various later waves. Spanish has contributed a considerable wordstock, too, though not nearly so large as French. Think ‘rodeo’, ‘corral’, ‘bronco’, and many other terms. More on this soon.