It's like any fighting game community. Go out, introduce people to the game, tell people who plays the game in your area to play with you if they haven't already. Having a public venue can definitely help since people may feel more comfortable at a public venue than at someone's house. It'll take time, but with enough dedication and time put into this, your local community will grow. If you have a local FGC in your city, then maybe ask them to add Melee or ask them how they made their community grow. Essentially you're gonna have to sacrifice Melee time to make the community grow. I'm sure there're more ideas out there.
