|This is probably not the most effective means of evangelization.|
To be fair, it is possible - though rather unlikely - for this happen. Why? Because it presupposes that the person reading your sign 1). knows that if refers to one of the canonical Gospels (and will remember to look it up); 2). that the one reading is seeking God; and, 3). that the reader has not already come to faith in the sole Redeemer of mankind. At the same time, it doesn't hurt to remember that "faith comes from what is heard" (Romans 10:17).
Every now again you'll even notice someone holding a sign that simply says "3:16":
Such a sign could cause even more confusion than those oval stickers you see on the back of vehicles that simply read "13.1" or "26.2" (don't pretend you haven't been confused by them):
It took me a long time - sometimes I'm a little slow - to realize they indicated someone had completed a half or full marathon, respectively (or at least claimed to have done so). (Before you ask, I only saw them while following someone on the road and could not read the small print as I drove.)
Even if a non-believer guessed that the 3:16 referred to a chapter and verse of the Bible (and remember the numbers when they were near a Bible), how would he or she know which book? What if the reader went to Genesis 3:16 (the first of the books), which reads: "To the woman he [God] said, 'I will greatly multiply your pain in childbearing; in pain you shall bring forth children, yet your desire shall be for your husband, and he will rule over you'"? That probably won't convert an unbeliever. Or what if the reader went instead to the last book, to Revelation 3:16, which reads: "So, because you are lukewarm, and neither cold nor not, I will spew you out of my mouth"? That not might not help, either.
In all of this we see the importance of reading (or hearing) a verse of the Scripture within the context in which it was written. What the posters ignore are the words Jesus proclaims two verses later: "He who believes in him is not condemned; he who does not believe is condemned already, because he has not believed in the name of the only-begotten Son of God" (John 3:18). Here we come to the crucial question of the Protestant Reformation: How do I know if I have the correct faith or believe in the right things?
Martin Luther rejected the nothing that "faith by itself, if it has no works is dead" (James 2:17). The Apostle James went on to say, "You see that a man is justified by works and not by faith alone" (James 2:25). Incidentally, this is the only place in the Scriptures where "faith alone" is found. Luther added the word to Romans 3:28 - it is not in Saint Paul's original text - because, as Luther himself said: "Dr. Martin Luther will have it so, and he says a papist and a donkey are the same thing" (he really wrote it, in his open letter on translating). Perhaps more politely, he also said, "Luther will have it so, and he says that he is a doctor above all the doctors of the pope."
In an attempt to be more convincing, he also claimed: "However, I was not depending upon or following the nature of the languages alone when I inserted the word solum in Romans 3. The text itself, and Saint Paul's meaning, urgently require and demand it."
If Saint Paul's meaning urgently require and demand the addition of the word "only," it is curious that the Apostle, who wrote under the inspiration of the Holy Spirit, did not himself choose to include it. He didn't include it, of course, because that would contradict the teaching of Saint James (whose letter Luther sought to remove from the Bible; he also wanted to remove Hebrews, Jude, and Revelation, in addition to the books he did remove from the Old Testament: I and II Maccabees, Judith, Tobit, Baruch, Sirach, and Wisdom).
All of that is a long way of saying that in order to know how precisely which or how many works he had to do to be saved, Luther simply threw works out and claimed that "faith alone" is necessary.
Reformers after him came along and wondered faith in what, precisely, was needed, or how much faith was needed. Their successors today have arrived at the notion of "once saved, always saved," claiming all that is necessary is the so-called "Sinner's Prayer." Saint Bonaventure, though, had a very different notion:
Now genuine faith excludes fiction and duplicity. For faith is fictitious when a person believes, but does not love or when a person believes and loves, but does not persevere. So true and genuine faith believes, loves, and perseveres, and all such believers will be saved.
- Saint Bonaventure, Commentary on the Gospel of John, 3.29
If one loves, one does; love simply must be expressed. Faith and works go together; our works are not unimportant or unnecessary. If they were not needed, Jesus would not have said, "You are my friends if you do what I command you" (John 15:14).
This is why Saint Paul did not simply say, "For in this hope we were saved" (Romans 8:24), but elsewhere wrote of "us who are being saved" (I Corinthians 1:18), and of how "much more we shall be present" (Romans 5:9). Saint Paul simply did not have an understanding of "once saved, always saved" because it is not truly Biblical.
Yes, God did so love the world that he sent his only-begotten Son to us. But Love requires something of us; he requires that we be continually converted and that, among other things, we love the least of his brothers by attending to their physical and spiritual needs, else wise we will not inherit his kingdom (cf. Matthew 25:31-46).