With somethings yes, others know. The only times I've had a problem with this is getting a woman to be honest about her intentions in a relationship. If I want something casual, she'll pretend that she's not looking for anything long term. On the other hand, if I'm look for something more serious, she will say and do things that both imply and directly state that she sees things as long term.
I often get flamed by girls saying "it's just because girls don't want to seem casual or they'll be labeled as sluts" or "girls don't want to look like they're just crazy and desperate for marriage and babies." Also, I'll get a girl telling me: "she just doesn't want to hurt you." It would hurt me more to find out that a girl who I had been seriously dating for months, who also said things leading towards a long term relationship just saw me is a fling. It also hurts when I find that a girl wanted things to be more serious or progress more quickly than they did. It hurts, because then I have to make the painful decision of whether or not to stick with such a, usually, good and sweet person. If I tell them to slow down, that would severely hurt, but it would have been avoided if they were honest.
So like I said, many girls will lie about some things but not others. It's not a black and white yes or no. But then again, maybe I've just been dating the wrong girls.