if you are planning a trip to Grenada, I would suggest staying in St George parish but closer to Grand Anse than St George's because Grand Anse is the longest and nicest beach in Grenada. As far as when to go, there's not really a better time to go because Grenada is a little off the beaten path. It's never as busy or as crowded in the tourist areas as some of the more popular Caribbean destinations.
it doesn't matter much where you stay since most hotels and resorts on the island of Grenada are great. The Coyaba Beach Resort is also located on the Grand Anse Beach and it's said to be one of the nicest places to stay on Grenada.
You can book a lovely two bedroom airbnb apartment in St. George's for about $32/night. Otherwise, I'd suggest staying at either Ade's Dream and Hotel Laurena, which are both very, very basic hotel rooms.