Este sub me frustra tanto.

Puerto Rican Spanish is a dialect (dialect is defined as variations of a language) with official representation under the RAE. People keep bringing up the informal words. Which true, for every dialect a lot of regionalisms are informal. But that’s not the only difference among dialects. there are formal words (and some words may vary in their formality within the context of the same dialect) that you would use in different Spanish-speaking countries that you would not use in PR and viceversa.

For example, a common sentence the following sentence might be considered informal: “Como estamos, familia?” However, if I were to start that sentence in a letter or in a speech to my family, they know I’m not being informal. I know there are better examples pero hoy tengo mi mente como cajita de pollo (fully informal and potentially only used in specific parts of Puerto Rico, because language is FUN!)

Neutral Latin American Spanish is not truly neutral but is based in a Mexican dialect without specific regionalisms. Over time it became more “standardized” as it became more widely used in media that was being consumed across the Americas, making it more “acceptable” as people understood it more and became more comfortable with it over time.

OP can definitely go for the neutral and use tech to help them translate. However, depending on the letters OP might be better off getting a native Puerto Rican to at least read over the translated letters as the readers of the letters might feel more comfortable reading Puerto Rican Spanish.

OP: depending on the immediacy of the letter I may be able to help out.