I find it interesting that all these terms of address; dude, guys, man, are all masculine forms, but becoming socially acceptable to use for women. However, I wonder how many men would be fine with me walking up to a mixed group of people and saying, 'Hi ladies.'
OP, I'm in Australia, and dude isn't really as widely used here as it seems to be in the US, so that probably colours my view. Dude, to me, is masculine and a bit juvenile, so I'd be a bit confused by someone using it to address me, but I wouldn't be super offended.