Our Garmin will choose the route depending on how you set it up. There are some set up choices such as; fastest (usually will be interstate), least amount of miles, which can be the slowest way, or just start going the way you sort of planned and it will re-calibrate and send you on your way. The Garmin is a really nice user friendly unit. We have a class C and sometimes it Does have problems finding a satellite in the cab area. My wife will move back to the dinette table with it if we really need to know when signal is lost.
You more than likely have a keeper, and Happy Birthday!
Brian