Piazza del Duomo is big and it is easy to find. You will by now be used to the fact that not everyone likes the bagpipes, so get in a pitch before the Old Bill turn up. Always be friendly and polite to them and you shouldn't get into too much trouble. It should be warmer in Italy at that time of year than it would be in Scotland, so you could well get an edge and pick up a few Euros. If you can't get a pitch in Milan, Como is about an hour away by train. I did some good pitches in the early evening there. The people are more likely to take a stroll at that time than they are in the middle of the day. Good luck and have fun.
Alan.