Just a short post for tonight, so please do ask me to follow up on this topic if you find it interesting. I was out on the Absolute Write forum today and the topic of language learning came up - one of the writers there was working with a character who spoke Arabic but was learning English, and trying to figure out how to portray her speech.
A number of people on AW gave advice about the sound structure or grammatical structure of Arabic - and it's true that the structure of a person's native language has an influence on the way that person speaks a new language. Others suggested that this writer go out and find a native Arabic speaker learning English to get a good language sample - certainly an excellent approach.
But there's more to the issue. It reminded me in some ways of the discussion of dialects we had here on this blog, because portraying speech errors in a sensitive way is equally difficult. The moment I think about altering spelling to reflect pronunciation errors, my internal alarm bells start going off. You can always go with word order, grammar and vocabulary usage, which is somewhat easier (and research on language learning sequences can help guide you on that). On the other hand, I had a character recently who gave me a lot of trouble, because he was supposed to be a native Chinese speaker who spoke perfect English but was putting on a strong Chinese accent. And every time I tried to contract his syntax, I felt I was losing the depth I wanted this character to have - that he was becoming to the reader what he was only pretending to be. In the end I went with greater language complexity, and a description of his accent.
The one thing that no one had yet addressed at AW (before I got there :) ) was discourse - the higher-level strategies that language learners use to get through a difficult interaction.
The first and foremost approach that a language learner will take in a tough spot is silence. I've been there - listening and listening but unable to respond. People often choose to stay silent in order to avoid mistakes. Another type of silence strategy is avoidance. Language learners will try to avoid grammar areas that cause them trouble, or vocabulary they don't know, by talking around the problem area. Avoidance also means that very often in conversation, language learners will make abrupt topic changes - when their resource pool for a particular topic runs out, they will switch to another (often without warning or explanation).
I would just encourage anyone dealing with language learners to remember that silence and avoidance are strong learner strategies - and best of all, they are among the easiest to portray in text without the risk of inadvertently ridiculing the learner.