There's nothing in the sentence that indicates the second subject pronoun "you" is used in the singular. The translation admits both forms: "אתה רוקד" "אתם רוקדים"; it may even be translated into feminine forms.
The English sentence uses "We", the first person plural pronoun, which can be translated as either female or male into Hebrew, thus, the correct forms are:
אנחנו יושבים (או אנו יושבים)
אנחנו יושבות(או אנו יושבות)