Hmm. I like it.
It sounds like you mean for this to be an angry, emotional scene. But I think you cop out slightly but softening your word choice. I mean, this kid just saw his old man with a hooker and he only refers to him as two-timing? What about a piece of shit bastard? And the hooker, would you really call someone that had an affair with your dad some Brady Bunch word like bimbo? What about a fucking whore? It just gives more power to the voice, portraying his distaste with raw emotion.
I don't know Kevin's age, but if he's at least, say, in double digits, those words are perfectly okay.
Also, the line, "He watched Topeka grow on the horizon, trying to shake the images in his head," is awkward. This means that he is trying to shake the image of Topeke growing on the horizon from his head, not that of his father naked and passed out.
You may also want to portray the fact he's on a bus sooner. I thought for the first paragraph he was driving, tears flowing freely from his eyes, as he looks at the rear-view mirror, glad to be rid of his father.
"The bus switched gears, hastening to its destination, growling as if preying upon it."
Cut the "as if preying upon it" bit. It's too much and it makes no sense.
"Reading had made Kevin tired too, but he found it impossible to sleep on a bus."
Cut out "on a bus." It's redundant, we know what you mean.
[This message has been edited by Swimming Bird (edited September 30, 2005).]