Acts 2 Dispensationalism is the view that a new ministry began in Acts 2 (following Jesus’ death). This new ministry included the gentiles, who were not included before that time.
Acts 2 Dispensationalism is not taken seriously by Biblical scholarship. It is interesting to note that critics of Christianity tell Christian history much like Acts 9 Dispensationalists (the gentiles given equal membership through the ministry of Paul and not before that time).
As I have noted, the Jews were active proselytizers even before Acts 2. Their proseletization included recruiting God-fearers in order to eventually get them to keep the entire Judiac Law, of which circumcision was an integral part. There is no indication the 12 apostles departed from this.
Greg Perry, of Disabling America fame, has a very good post critiquing Acts 2 dispensationalism. One key point Perry stresses is asking when the gentiles started showing up in the book of Acts. The entire post is worth reading: