I realize I have wrestled with this question quite a bit lately, but I ought to address the Jerusalem Conference and Galatians one more time since I ran across something interesting on the issue.
In Polhill’s chapter on Galatians in Paul and his Letters (Nashville: Broadman & Holman, 1999) it is less than clear if he believes that Galatians comes before or after the Jerusalem council. He gives both sides of the argument and deals with Galatians after the council. I was under the impression that he was opting for the later view, which he states clearly as his view on page 111 of P&HL. In his excellent commentary on Acts, he says “Although the two accounts contain significant differences, the similarities seem to outweigh these, and it is probable that they relate to the same event” and a bit later “it will be assumed in the commentary that follows that Paul and Luke were referring to the same conference” (Acts, NAC 26; Nashville: Broadman & Holman, 2001) page 321.
However, John Pollhill also wrote the notes on Acts for the ESV Study Bible. In this shorter commentary on Acts, he states “Though some scholars think that Paul is referring to this meeting in Gal 2:1-10, it is better to see that passage as referring to private contacts made during his famine relief visit to Jerusalem” (ESVSB, 2114). I suppose this indicates some change of thought for Polhill on the chronology of Acts and Galatians.
It is good to know that scholars develop their ideas over time.