Heyo! I used to run into this situation pretty often, especially while in film school, but as I've grown professionally I've realized that more often than not the problem is not the director's inexperience / poor opinion / limited budget etc., but my own failure to totally grok the experience they're trying to craft.
Here's the important thing: Ultimately, it's the director's film, and what they think sounds right is much more important than what you think sounds right. They're the lead creative force behind the project, and if they're making uninteresting or cliched sound decisions, you have to either re-evaluate your understanding of what this movie is supposed to be, or you have to convince the director of why your particular decisions are the right ones for the movie they're making.
What doesn't work is just saying something's a bad decision, or doesn't sound good, or isn't the way things are done. Every project is different, and the director knows that just because something is "wrong" for other projects doesn't make it wrong for this one. You have to come at it from their perspective, and really focus on why a particular decision doesn't work for this particular movie.
Finally, it's crucial that you and the director be making the same movie. Disagreements are healthy as long as they ultimately either enlighten you with an aspect of the director's vision you hadn't considered, or enlighten the director with a way to achieve that vision they hadn't considered. If you're having a lot of disagreements, then before becoming frustrated with the director you should think long and hard about what it is that you're not getting about their vision. And if even after that you think the director's wrong, be prepared with rationales specific to this film, this audience, etc.
But I'd recommend absolutely stating your opinions and being prepared to learn something. If you don't voice your disagreements, the collaboration is doomed because you're idea of what this movie should be (sound like) don't match the client's.
Sorry for the long post. My 2cents :-D