Well, heck yeah!!
What's wrong with scoping out some awesome eye candy like the girl in the photo above?
That's why dark sunglasses were invented!! Mirrored sunglasses are better IMO. If the subject doesn't appeal to you, your eyes won't give you away behind sunglasses. Now if the subject is smokin' hot, and you're definitely interested, then sliding those things down and exposing your eyes and looking at your subject like they're a walking god/goddess is a very high compliment.
Sunglasses are your friends. :biggrin1: