Building a mobile version for a custom theme

I have a custom theme I built for this site:
http://www.broadstreetvet.com

I want to make a custom mobile theme for it as well. I have tried a few plugins but since I am using several different page templates they don’t work very well.

How do I include alternate style sheets for a wordpress theme?
I’m using this code:

<link rel="stylesheet" href="<?php bloginfo('stylesheet_url'); ?>" type="text/css" media="screen and (min-width:481px)" />
<link rel="stylesheet" href="<?php bloginfo('template_directory'); ?>/css/mobile.css" type="text/css" media="only screen and (max-width: 480px)" />

but I get no change on my iphone.

Thanks!