If the situation has deteriorated to such an extent that fleeing becomes necessary, why do you believe Garmin’s GPS service would still be functional?
It may or may not be. Leaving familiar terrain in a societal breakdown sounds suicidal to me. The only way I’d consider it is if remaining where I am removed all doubt and the mere possibility elsewhere would be an improvement.
I take it that you don't live in or near NYC, LA, or NO then.
Also, what if you needed to go rescue a loved one or friend and get them to safer area? For a few hundred bucks, it could prove to be a life saver. That's my call and what your personal equipment list consists of is certainly up to you.