It doesn't bother me if others give hints or clues to where the cache is in their own comments, just as long as they encrypt that part for those that do not want them. Sometimes, when I am having trouble finding a certain cache, it helps me to read the comments others have left. However, I do not feel that it is ok to give hints/clues in your commenst without encrytpting them. It is not ok to ruin the hunt for someone else by blabbing where it is without encrypting those comments. Of course, if in the description of the cache, the owner asks that you do not leave clues/hints in your comments, even encrypted ones, I would respect his/her wishes.
I am one of these people who would get completely bugged when I cannot find a certain cache that I have searched again and again for. I have not done this yet, but I don't see anything wrong with contacting/sending a message to the owner of the cache for a hint. I just recently placed my own first cache and I would hate it if a person searched several times for it and never found it. I think you should search, I mean really search, for the cache at least 3 separate times before contacting the owner about a hint though.