The Desert Mermaid

I like that! It's a lot more flexible than some of the other methods I've seen in comics (and actually in straight prose, too--Terry Pratchett uses Death's unique typeface to full advantage). My only concern there would be that readers could stumble over it if it gets too complicated--but I'm guessing that most people in your story would speak with similar accents, so you won't wind up with a different typeface for every person.