Picking up my first Prius 3 this weekend. What is needed to get traffic on the nav?

You'll need to down load the Entune application to your iPhone. You'll need to visit www.myentune.com
Enter the VIN# for your new Prius, your name and email address as well. Entune will send you an email confirmation with a link where you'll then create a password.
Your Entune account is activated.

When you pick up your car, bring the white apple cable along, you'll need to plug into that USB with your iPhone, launch the entune app and log-in with the email address and password that you used to create the account.
Pair the bluetooth, then launch the Entune app on your iPhone. Be sure you select connect on your iPhone's Entune app if it doesn't connect on it's own. It's the gear looking icon on the bottom right of the screen. You're connected to the new when the iPhone screen shows a red "Disconnect," button.

No teathering, use the cable...yes, yes I've read that a tethering enabled iPhone will work, but just cable in. Your iPod will sound better, you'll have better control over the playlists and can even call up an artist or album with the voice recognition. Did I mention you'll be charing the battery too?

The traffic data will be active on the maps so long as you're logged on and connected to Entune. You'll see the green and red highlighted roads much like gougle or XM. Ther's also a "TRAFFIC," app in the APPS screen that will show traffic occurrences around the area.

I can't say weather 2Gigs is enough. If you're using basic traffic and weather data...then you'll be fine. If you're streaming Pandora in the car, at work and at home then you might not have enough.
Your phone has a data meter, just monitor it. I wouldn't spend the money on a bigger data plan until you understand your monthly use.

 

The nav doesn't require a cell phone connection at all. No bt or data connection.