Writing a novel and short story about a northern English girl (Mancunian with some Scottish and a few Lincolnshire words, which most critics seem to treat as a foreign language) who lives in Guatemala and speaks fluent child-Spanish, with other characters speaking Spanish, this issue is either dear to my heart or the bane of my existence. I am absolutely certain I have got stories rejected on this issue alone.
At the same time, I must say that the idea that Scots, Lancastrians, Yellowbellies (from Lincolnshire) let alone Guatemalans, should speak the Queen's English or American English, to make life easier for lazy readers, is at least as offensive as sexist or racist language. I believe that people, even characters, because they represent people, deserve respect. We should respect dialects and preserve them because they could easily disappear in this globalising world. Then we will be much poorer folk.
I am afraid that I cannot give any prescription because I cannot claim that I have handled this successfully enough to advise others. I shall just share some thoughts.
Ideologically, I am closest to Grizzly. I have also received this advice from critics from time to time. Weighing in on that is a host of books (I can supplement with examples if requested) from Trainspotters to A Clockwork Orange, which have thrown readers into the sea and told them to learn to swim quickly and yet become best sellers.
The problem is that ideology is for an ideal world. I am quite concerned that, if I insist on that ideal world, as a new writer, experimental in many other ways too, I shall never get published.
I started with a novel manuscript about Belgians growing up in the Congo in the 1950s, called "Poisoned Dreams". I handled the language issue by letting the characters speak French but then put the translation in brackets. Example: Je ne sais pas etre belle ("I could never be beautiful."). The rejecting Editor said "We're not sure the bilingual writing works." and critics also panned it. They said it "broke the flow" of the dialogue and distracted the reader.
Then I tried with no translation, for French (Belgian or Quebecois), Spanish or English dialects (northern English or Canadian). My most common comment: "I couldn't understand the foreign language." It caused them to think that the English dialects were also a foreign language!
In my novel, New Little Princess, I have used an entertainment reporter, from Buckinghamshire (so he speaks the Queen's English naturally) as narrator. He can explain what the Princess says in northern English, e.g. "What do you mean by 'buzzin''?" asks Anthony. "You know, 'buzzin'', like over the moon," says the Princess. "You mean 'very happy'?" says Anthony "Aye, got it!" says the Princess. It works but it stretches out the dialogue. Readers might get bored, with so much ado about one word. Anthony is useless for Spanish and he is not always present, so that solution doesn't work all the time.
My latest compromise, which you can see in my currently posted story, "My Holiday In Guatemala", is to try to put the translation right after the Spanish. Example: "If I’m not a hit in Lincoln Park, it will be 'Hasta nunca, Princesita!', see you never, little Princess, from Pina Colada." This is Shunn format, so the publisher will change underscores to italics if it is published.
I have had some rejections already with that story, so I don't know if that solves the problem or continues it.
That is all that I can say now about it but I am certainly drinking in your comments on this thread.