The general guidelines I've read about for women say that you should ensure you're covered from your shoulders down to your knees, i.e. a top with some form of sleeve and not too low cut, and shorts/skirt/trousers that go below your knee.

Personally I think it's good to stick to these guidelines out of respect for the conservative nature of the country you're in, but you'll see lots of people who don't. As people have said, you'll get reactions whatever you wear, but you may provoke stronger and angrier reactions if you "let it all hang out".