Is it a common view among Christains that Satan is the lord of this world? As I drove past a church (not sure the denomination) on a country road, the sign out front read "Satan is the lord of this world. Be careful!" Is this a widely accepted view?

If so, how do we explain Matthew 28:18-20 where a resurrected Jesus says "All power in heaven and on earth has been given to me"?
According to apostle Paul in Bible, Satan is the "god" of this world 2 Cor 4:4 
However the term "god of this world" means the ruler, the one who is being worshiped or obeyed. Satan got that title by deceiving the first Adam and leading him to sin against God (Genesis 3).

However like you said at the resurrection, all power was given to Jesus Matthew 28:18-20 and he gave us back his (power) name (to the church, every born again believer) and at the mention of the name of Jesus that we have received EVERY knees shall bow in heaven, on earth and under the earth Philippians 2:10. Which means, Satan is the "god" of this world and we (born again believers) are "god over Satan and the World". That is why demons flee when we cast them out using the name of Jesus.

In a nutshell, those who have accepted Jesus as their Lord and Savior (Rom 10:9/John 1:12) are the "god of this world". They have authority. So, the church sign board that you saw.. It depends on what they meant by Satan being the Lord of this world.