Does the Holy Spirit have to open a person's understanding before they can be saved?
Yes. Every person who comes to a saving knowledge of the Gospel must have their understanding opened by the Holy Spirit. The Lord opens the heart in the person of the Holy Spirit, and this has never changed. The Holy Spirit is omnipresent, approaches every soul, so no one can claim He never approached them.
Les explains that in Philippi, Paul was the proclaimer speaking for the Gospel, but before the Jewish lady could comprehend it, the Lord had to open her heart in the person of the Holy Spirit. Les says that has never changed: every person who comes to a saving knowledge of the Gospel must have their understanding opened by a work of the Holy Spirit. That work is there for everyone. No one can say the Holy Spirit never approached them, because He is omnipresent, everywhere, and misses not a soul. Les connects this to John 1:9, where Christ is the true light that lights every man coming into the world, and to Romans 1, where no one at the Great White Throne will ever say they never had a chance.