It depends on how you say it. You don't want to say anything that is suggestive, overly forward or said in a nervous and serious way. Telling someone you think they're cute isn't illegal but like skyDancer said, there's no guarantee it will be taken in the way you intended. Most often you can communicate the same idea with a smile and a friendly attitude without risking saying something that would offend.
If you must say something try, "I hate to see you go, you surely improved the view at this school. " :-)
Answered Dec 16, 2011
Edited Dec 16, 2011