Portraying regional dialects, accents, and rude language

How do you and should you even bother including regional dialects and foreign accents in stories? I do not much like the over use of apostrophes and words written phonetically. I was thinking about Shampoo (who is Chinese) and Ukyo (who is from the Kansai area not Tokyo like most of the cast). How would I go about portraying their dialect/accent?

For Shampoo I would most likely just have her use Chinese words occasionally and try to explain something but be unable to think of the proper word. I would not have her use Hulk speak (speak in third person, skip articles, baby like talk, etc). She does not do that in the original though her Japanese is not good and it is shown to not be good. Talking like she is portrayed to sometimes in English translations, would in Japan not be viewed as speaking the language poorly, it would be viewed as being cute (kawaii) and was how Azusa talked.

For Ukyo though I really do not know how to portray her regional dialect. The setting is Japan and she would still be speaking Japanese (though I'd be writing in English) so doing that to convey it would not really work. Having her use aho for idiot instead of baka, or using the honorific -han instead of -san, works in Japanese but would not work in English, since honorifics are different in English and neither aho or baka are words in English. I could arbitrarily choose a different regional dialect but there is not a regional dialect that would make a good substitute (though I'd probably choose British English since other than my own dialect it is the one I know the best).

In addition to those how should I portray ruder language? I ask this because Ranma occasionally uses pretty rude language, VIZ decided to show this in the manga by having him use truncated or phonetically spelled words (ta for to, ya for you, etc.) but only sparingly and generally when Ranma would have used ruder language - times he is upset (some authors of fan fiction have him say things like using ya for you every time and it really annoys me since it makes Ranma look dumb and slow - which he is most definitely not, is extremely distracting, and is not even how VIZ had it - this is particularly annoying if you read another VIZ manga such as Tenchi Muyo and see Ryoko and even Sashimi occasionally use the exact same phonetic words as Ranma yet those authors who have Ranma say them only have Ranma use them and none of the other characters). The obvious solution would be to have Ranma actually use ruder language such as swear words, but some people may find that to be jarring.