You cannot get this cache by car. you will need to go by bike or foot. I reccomend taking a bike ride through the greenway, as it is most enjoyable and pretty far of a walk to reach GZ
From SW N River Drive, as you head South and are near the I-95 overpass, you will notice a gate to your right along the Miami river. This leads you to the Miami River Greenway path. The path is accessable from sun-up to sun-down. Go through the gate and make your way down the path and along the river to GZ, at the very end of the path. Sit on the last bench and enjoy the spot. you are very close to the cache.
Enjoy :)