Yeah, it is pretty much safe here, until like 10pm... then there is a few gang hotspots, but if you don't cause any fuss and stick to mainstream areas you'll be right.
We don't really have downtown/midtown, it is just the CBD (Central Business District) surrounded by fancy inner suburbs, then outer suburbs.
Guns are rare here, mainly used by Italian gangsters, but they kill their own. You're safe from them. Asian gangs use knifes, but they are in the western suburbs mainly, so keep clear of there.
Our police, they are pretty much non-existent. They are more concerned with giving speeding tickets than dealing with punka*s kids, so they won't bother ya.
Yep, we have a train system, you only have to buy a ticket if you want to get of at one of the city stops, all the other stations you can get out without needing a ticket. Stations that I'm pretty sure you will need a ticket for: Flinders Street, Spencer Street, Parliment, Flagstaff, Melbourne Central, Richmond.
You can ride trams without having to buy a ticket, inspectors are a rarity.. If you see one coming on, you just get up and start purchasing a ticket from the machine. Alternatively, you can just carry an unvalidated ticket and validate if need be. If anyone questions you, just say your from America and don't understand our system.