I get confused at whose talking a lot in the dialogue. I suggest you differentiate it more. Otherwise I've been able to keep up with the narration.

As for the plot/setting, I don't know how to explain it, but throwing in all the tribes, aside from the Crow characters, gives it a realness, I guess you could say. The only thing missing is the insulting Indian humor we use on each other.

I also like the little things mentioned for horse riding - from the clothing to putting on a saddle. It shows it to be a lot more of a skill than just jumping on a saddle, and having some humorous experiences riding I know first hand.

I like it, especially since you don't got Natives in it acting all stereotypical. The only thing I have to suggest is make some of the dialogue sound more natural, it feels a bit too polished; but since this is like a diary, I could see one recording it more formally - if you were going that route.