They went in and preached the Gospel, but they did not stay in the synagogues and make them their permanent home of worship. Let them come out of the RCC and minister to Catholics. I think you would be very hard pressed to find a Catholic church that would let a born again former Catholic come in and preach boldly as Paul did in the synagogues. Not to mention staying inside would not be conducive to spiritual growth in the new believer.
I don’t believe the Spirit would ever lead someone born again back into a church like the RCC as a permanent place of worship...Paul was not taken to a synagogue after his encounter with Christ....he was taken away for three years to Arabia and taught by Jesus Himself. There would be no spiritual gain whatsoever for a new believer in staying where he was converted. One must be grounded in the faith and this could not happen in the RCC. This is why all the former Catholics come out of it and yet are still able to minister to Catholics.
I do not believe there are born again believers in a Catholic church. And those who say they are do not know the meaning of born again. When I listen to the testimonies of former Catholics who came out of the RCC, it is such a stark contrast between what they had before and what they have after the RCC.
God would not leave them in a place of spiritual deadness.
http://youngkerux.wordpress.com/tag/apostle-peter/
Since it is not unusual for someone to speak in the synagogue or lead in the reading, the Lord Jesus and the Apostle Paul took that opportunity to preach and teach in the synagogue. The Lord Jesus would regularly enter a synagogue in his preaching ministry and consequently earned the reputation as a “teacher” especially after teaching with distinct authority unlike the scribes (Mark 1:21, 22). Unfortunately, the people only thought of him as a good teacher and not as the Messiah Himself. The Apostle Paul reasoned, persuaded, disputed, and spoke boldly in the synagogues city after city. One of the fruits of this labor was Priscilla and Aquila (Acts 18:26). Both the Lord Jesus and the Apostle Paul took the opportunity in their cultural setting to minister to people’s needs and to preach the Gospel.
If He engineers such circumstances in my life, then that is where I will be standing firm in Him and witnessing about Him.
Strangely, such circumstances were the subject of today's Oswald Chambers devotion:
Are you going on with Jesus? The way goes through Gethsemane, through the city gate, and on “outside the camp” (Hebrews 13:13). The way is lonely and goes on until there is no longer even a trace of a footprint to follow— but only the voice saying, “Follow Me” (Matthew 4:19)