There are basically two kinds of people who are alive on earth, the living and the dead.
The living are believers in what God said about Christ Jesus. They have the deposit of the Spirit. They have been born again. For those people, to die is to leave the body and be present with Christ.
We are confident, I [Paul] say, and willing rather to be absent from the body, and to be present with the Lord.
2 Cor 5:8
For to me [Paul] to live is Christ, and to die is gain.
And if I [Jesus] go and prepare a place for you, I will come again, and receive you unto myself; that where I am, there ye may be also.
The dead are people who have not heard of Christ who have not been born again. For these people, to die is to await the great white throne judgment of God where they appear.
And I saw the dead, small and great, stand before God; and the books were opened: and another book was opened, which is the book of life: and the dead were judged out of those things which were written in the books, according to their works. And the sea gave up the dead which were in it; and death and hell delivered up the dead which were in them: and they were judged every man according to their works.
So, it is true that after a person dies they will meet God.
PS. The billboard was trying to convince the dead on earth to be born again because they were taught that once you are dead you do not have a second chance to believe what God says. The bible, however, says this about the great white throne judgment.
The books are opened and the book of life is opened. The dead are judged by their works in the books. All will fail because works are as filthy rags before God.
Then what happens? Death and hell are cast into the lake of fire which is the second death. And the dead who were present?
And whosoever was not found written in the book of life was cast into the lake of fire.
Can they not as we have done here say I'm a sinner, my works born of my pride mean zero, I repent, I believe you God?