It's totally fine as long as you're mindful of who you're saying it to, however that might be more of an issue of tone than it is of offending people for using gendered speech.
To break it down, you would be totally fine saying something like "are you guys coming?" to a group of guys, to a group of guys and girls, or even a group of girls. If it's just a group of girls you can say "you girls" or "you ladies" or whatever you prefer, but guys is acceptable.
You cannot use "guys" generally to refer to women in all situations. For example, if you were to say "I went out to dinner with some guys from work" I would assume that it was a group of all men. In fact there are plenty of girls who take pride in being "one of the guys," which means they think they are treated like a "guy" when in groups of male friends.
If you're worried about making a mistake with it, just keep your references to girls as "guys" to the phrase "you guys," and use gender neutral words for the rest. I think that in general that rule should hold true, with anything other than "you guys" having a distinct masculine connotation, with some room for a few exceptions.