get a dark colored domke f5xb cut off the domke labels, wash it everytime you do your laundry for 4 months before you go on your trip, or buy a used one that looks like it's been to a warzone and back.....plenty of used ones on ebay, hell i'm selling one right now, real cheap. Get the waist belt and use it with the shoulder strap (can't be grabed off your person), Use a mini combination luggage lock on the zipper pulls.
If you're paranoid about camera getting stolen, buy a Zorki 6, canon 50mm f1.8 and 35mm f2.8, and a Voigtlander 28/35 mini finder. there you've got a camera that cost nearly nothing compared to a leica, has wide baselength for night focusing. Youv'e also got 2 decent lenses that yeild nice results yet are relatively cheap. And if it still goes missing, you're only set back $250 ish dollars.....
dress:
don't wear sandals, tourist trademark in many parts of the world, don't wear shorts.
avoid high fashion jeans, stick with levis in plain blue, or some kakhis or even black slacks. wear plain colored buttion shirt, loos the sunglasses and hats, loose the expensive wrist watch, wear a timex or skagan, dark colored.