Hi Diane, Paul seems to be using relative "human terms" in his statements about saving people. We all know that it is absolutely God who does the saving, but He uses people as a vehicle through "the foolishness of preaching" to save them that believe. God could do it Himself, but He chooses do it the way He does.
God provides the preacher.
1Co 1:21 For after that in the wisdom of God the world by wisdom knew not God, it pleased God by the foolishness of preaching to save them that believe.
Then He also provides the faith to believe what the preacher is teaching.
Eph 2:8 For by grace are ye saved through faith; and that not of yourselves: it is the gift of God:
Eph 2:9 Not of works, lest any man should boast.
Therefor, all is still of God.
You are right also in saying, "it is because of by hearing what Paul says that some will be saved". Both the relative and absolute can be and are true.
Also I think you got it right about the "flesh" being the Jews. Some translations use "my people".