The first half of the Gospel According to St. John is sometimes called the Book of Signs, since it structures Jesus' ministry around the frame of a series of seven signs:
The turning of water into wine at Cana
The cure of the royal official's son
The cure of the paralytic at the pool
The multiplication of loaves
The walking on water
The cure of the man born blind
The raising of Lazarus
One of the lessons implied by writing of Jesus in this way is that, as disciples of Jesus, we ourselves are signs.
Note that I didn't write, "we ourselves are to be signs." We don't have a choice in the matter. We are signs, whether we like it or not. Just ask Lazarus, whose life was plotted against because, merely by being alive, he was a sign of Jesus' power over death.
What we can choose, individually and communally, is what we are a sign of.
Am I a sign of God's love for the world? Of His power to transform lives, and even to bring us into His own eternal life? Or am I a sign of His indifference, irrelevance, or even hatred? Am I a sign that God is just another god, Whose followers do as the pagans do?
Most of us, I'd guess, are mixed signs, changeable and confusing to those who read us. That's the human condition, but it's still a false sign, because God Himself is steadfast and clear. We are to strive to become perfect, not out of fear of damnation, but because anything less than perfection is a false sign of our Lord and Savior. Or, as Jesus said of the man born blind, so that the works of God might be made visible through us.