"Naughty" will depend on context.
It has different meanings:
Michievous/slyly teasing - travesso, ou uma palavra mais antiga "danadinho" -apesar que muitos não gostam dessa palavra pois pode trazer analogia com "danação". Mesma coisa com "aquele que faz diabruras" alguns preferem "aquele que faz travessuras". Contudo se a criança for igual ao Dênis "O pimentinha" do filme, talvez se use a palavra "mischievously impish", evil, bad, etc.
An hiperactive child could be called "unruly" (in old times) but more comtemporary days perhaps you read/listen the words "overactive/hyped-up/excitable/hyper/abnormally or usually active" and other descriptions as well.
I don´t rule out the use of the word to refer to adult persons or animals, perhaps in some colloquial (almost joking) way, but I must point out that "naughty" is usually used to mention young people with nonconforming (even if not by design, sometimes) or plain wayward (non-standard) behavior!
Some people mention Miley Cirus and the word naughty in the same sentence, meaning that she wants to impress the public in a cheeky (inpudent) and through hypersexualization. Some would find it positive, others less so, depending on the audience. Miley Cyrus Brings Her Naughty Side - And Her Sister - To The Summertime Ball!http://www.capitalfm.com/artists/miley- ... 4-setlist/Resposta mais sucinta:
pode ser um ou o outro significado (dentro do contexto).