^ When your Android phone is paired with a Bluetooth audio device, all audio is sent over Bluetooth. What this means is your nav instructions are sent over Bluetooth instead of playing through the internal speaker. So, if you use Bluetooth audio to listen to music on your phone, you will get the prompts.
That's how my HTC Sensation 4G works, anyway.. I presume all devices should work that way.
Congrats on the new ride, btw. I broke 200 miles since Thursday earlier. :)