I guess the phone doesn't know or care if you subscribe to the hotspot feature. It only wants to login and errors out if it can't.
Go to the Marketplace and search for an app called GPStest. This will show how many satellites your phone is seeing among other things. At least you can see if the GPS is working this way.
Don't know about Navigator. It was always free to use on my Evo. I thought it was the same on all Sprint phones?