I tend to go wherever I need to. I guess island 4 and 3 are my main two places (for breeding).
Put them in the daycare and run around on Three Island. Fly back every now and then to see if the man has moved.
However, I NEVER return to Pallet after I complete the game. XD
5 island, i'm getting ready to whoop the elite 4 again. after all my pokemon are level 60, i'll start training in cerulean cave and catch mewtwo if i feel like it. i tend to be in vermillion and 5 island a lot for no particular reason, although i used to hang around kindle road a lot in the area near ember spa with all the fighting type trainers.
4 island for breeding but i dont hang about there. i guess the BEST place to hang about would be celdaon for the game corner, but i must admit ive taken a liking to 3 island. i dont even know why, its not THAT interesting..