Maps of Grenada

The best map, and the only one really suitable for country walking, orienteering etc is the British Ordinance Survey map last edited in 1992 and now out of print.  Specialist map sellers still have copies, and photocopies of the nicer original can be purchased from various gift shops.

Your hotel or car renter will probably give you one of several quite serviceable alternatives for driving.

There are a few online maps available too. 

Travelgrenada's interactive Grenada map 

Travelgrenada's St Georges map 

Travelgrenadas Grand Anse map

For use on the island, your smart phone / tablet can of course use Google or Apple maps.  If you seek a data free solution (dont want to use data roaming $$$ or buy a local data sim card $$) there are apps like Ulmon CityMapstogo that will download a map, and guide to the whole island  for you to use, with your GPS.