I live in SoCal where trailhead car burglaries are more common. I never leave anything visible in my car. Furthermore, I even empty my glove box and leave the door open.
Also, I don't use a suction cup on the windshield for my GPS mount (illegal in Cali. anyway). When the crooks see the ring left on the glass when it is removed, they will assume there is a car GPS or radar detector inside.
If you leave your car relatively "sterile" with no targets of opportunity visible, the scumbags will move on to the next one.