Once the husks turn brown, they should be ripe. They are edible. I have read articles that say if they have a bitter taste, don't eat them. They should have a tangy taste and make great salsa. I use the store-bought tomatillos to make a "salsa verde" with oven roasted tomatillos, jalapenos and garlic. Once they all have a slightly blackened crust on one side, turn them over and blacken the other. Throw them in a blender, then add finely chopped onion and cilantro to the blended mix when you pour it out.
OMG, I'm making myself hungry...