yes and no.
to completely disregard artist intent and his or her background is to throw away the key to unlocking further understanding of the work.
yes, the viewer...or to be relevant to this thread LISTENER'S interpretation is valid, but in my opinion it doesn't completely trump the artist's intent.
You go and tell Bono that the song Lemon is about a kid at a Lemonade stand day dreaming on a hot summer day and see what he tells you. It may mean that to you but its not the original intent of the song. So who's correct?