Says Mark Twain, "When a personage talks like an illustrated, gilt-edged, tree-calf, hand-tooled, seven-dollar Friendship's Offering in the beginning of a paragraph, he shall not talk like a Negro minstrel at the end of it." I'm going to say right here, if you don't know how to write a dialect properly then don't try fudging it. Write the speech out like normal and say that it was said in a particular dialect.
For example, "'I heard you were checking out of the hospital today, so I came to pick you up,' the man said in a southern accent." Writing in dialect requires a basic knowledge of how words represent particular sounds. It also requires one to have heard enough of the dialect to know the patterns each dialect has. It is not fun reading badly written dialect when you know how it sounds and those who don't know how dialect should be read in the first place will only become even more confused.
That said, don't ever call dialect writing a misspelling and/or grammatical error. I had someone who was a high school senior write in an author's note to pardon the bad grammar, because it was being done for a humorous effect. I've covered in the first chapter how grammar isn't something one should joke about, it is serious business, so I was far from pleased in the review I left him, only to find out that he thought dialect was actual spelling errors.
Which then amounted to me realizing that he felt that using dialect amounted to adding humor to the story. I can't think of many times that it actually does, and the times I can think of it doing so the dialect is simply adding to the characters already humorous personality. So a person really shouldn't mess with dialog unless they know what they are doing.
Because while dialect is in itself not a misspelling or grammar issue, you can actually misspell a particular dialect and find yourself just making your readers even more confused.