Yes, you can wear jeans in Milan. Milan is a city that loves its fashion. It's also a city that hates its fashion. If you want to get a sense of what Milan is like, just walk around the city and look at the people. They're all wearing the same thing: black t-shirts and jeans. They wear those jeans with sneakers or boots (or both!) and they wear them every day—sometimes multiple times a day—but they still manage to look like they've just gotten off the plane from New York City or London, which is kind of impressive!