The ladies would be the ones to say definitively, but I would tend to think that as long as it's only compliments you're offering, there should be no problem. Even stuff like "nice rack!" will usually be ok, as long as the woman in question knows you're just complimenting and not perving on her (like me!)
You know what women are, with regards to compliments, according to Homer: "Greedy, ravenous monsters always wanting more, more, MORE!!!"
Seriously though, I doubt any woman (or man) here would take offence to being called pretty, sexy, fine, whatever. We're not that PC!