Okay, this is what fixed it for me since I'm using MAMP Pro. Use the following as your path when previewing your site in the browser: (obviously fill in your info where appropriate)
http://yourhost.yourIPAddress.xip.io/fileName.php
In DW's site manager inside your localhost server settings, set your Web URL to http://yourhost.yourIPAddress.xip.io/
Using virtual hosts, I'm now able to tether all devices together successfully. For more info on xip.io check out this link:
http://xip.io/