Translation:Let's get ready for some fun.
Do Brazilians really use the sentence, or is it just a translation of the English ?
Not really.. seems fony to say it like that. The closer I can think is Vamos nos preparar para se divertir. But we would use something more specific, like para sair (go out), para ir no cinema (go to the movies). Nos preparar would also be more specific, like nos vestir/arrumar (get dressed).