This will surely come as a surprise to those who know me best: I've come to judge as correct a minority position with regard to the timing of the events described in Gal. 2:1-10. I am convinced that these occurred during Paul's second trip to Jerusalem, recorded in Acts 11/12, rather than his third, recorded in Acts 15. The following is my reasoning.
If Acts 15=Gal. 2:1-10 then we have to assume the following. First, that Luke omits a reference to the prophecy that took Paul to Jerusalem in the first place; second, that Luke introduces a trip to Jerusalem unknown from the Pauline literature. If Acts 11:27-30=Gal. 2:1-10 then suddenly we have Luke referring to a prophecy which takes Paul to Jerusalem and locating this during Paul's second journey. Moreover, if we look at what takes Paul to Jerusalem in Acts 15 it's a conflict in Antioch, focused upon Gentile inclusion in the new movement (cf. vv. 1-3): exactly the sort of conflict described in Gal. 2:11-14. Put quite simply, the data coheres better, and provides a ready anwer to the question: "Why does Paul in Galatians mention only two visits when Acts narrates more?" Simple: only two visits had occurred when Paul wrote Galatians. Frankly, as far as I can tell, the only reason to think that Acts 11:27-30 can't equal Gal. 2:1-10 is an argument from silence: Luke doesn't mention that Paul discusses such matters with the leaders in Jerusalem during his second visit. I don't think that's sufficient to overturn the coherence that occurs if we imagine Gal. 2:1-10 describing events that occurred during the second Lukan visit and 2:11-14 describing the struggle that leads to the Jerusalem council (alluded to in Acts 15:1-3). As such I would suggest that he wrote the Epistle to the Galatians in the period immediately running up to the Council of Acts 15.
It is perhaps a datum of some further interest that, according to Acts, immediately following the Council Paul went to what would be considered southern Galatia. I suspect that Paul had heard that the controversy with which he was struggling in Antioch had spread to the churches of that region, so before the Council he writes a letter and after he goes to check on them in person. If you consider that the controversy that took place in Antioch could have arisen in southern Galatia more or less simultaneously (i.e. it didn't have to necessarily start in Antioch and spread to southern Galatia) this hypothesis requires little more time than that which Paul would have needed to draft his letter. The time frame supposed by Acts 15:2 is sufficiently ambiguous to allow for such a relatively brief amount of time.
Getting more specific with regard to time, we need to remember that Luke is remarkably inexact with chronology and here even more so than usual. This means that we have to rely upon other sources to get a better sense of the absolute dates of these events. Luke has Paul and Barnabas being commissioned to go to Jerusalem before Agrippa's persecution of the church in, probably, 41. He then has Paul and Barnabas returning after Agrippa dies, in 44 (cf. 12:24-25; some variants read that they return "to" Jerusalem and some "from," and given the fact that they are next located in Antioch the latter seems to make better sense). That trip could have been anytime in that range, or potentially even some amount of time after Agrippa dies. Here is where Galatians very much helps us. If we suppose, as I think likely, that Jesus died in 30 and that, following Harnack, Jewett, and Riesner Paul was converted approximately eighteen months later, then Paul was converted in 31. If he went up to Jerusalem two to three years later (the "three years" of Gal. 1:18, reckoned inclusively), and a second time eleven to fourteen years after that (the "fourteen years" of Gal. 2:1, reckoned inclusively and dated either from the conversion or from the first visit), then the events of Gal. 2:1-10 take place thirteen to seventeen years after his conversion, i.e. sometime between 44 and 48. Given Paul's itinerary as described in Acts 16-17, and the fact that he spends eighteen months in Corinth before appearing before Gallio sometime between July 1 51 and June 30 52 (cf. the Gallio inscription), it seems to me that 48 remains the best date for the Council, although or year or two in either direction is possible. If we suppose 48, then permit perhaps 47 for the travels in southern Galatia before the Council, then we have the second visit in perhaps around 46. Again, though a year or two in either direction is altogether possible.
The above of course supposes a fairly high degree of confidence in the Pauline itineraries given in Acts 13-18. I can defend this supposition, which is not assumed arbitrarily but rather is the product of antecedent investigation. That, however, would be an altogether different blog post.