Here's how you can respond:
If you are leaving:
* Oui, j'y vais. (Yes, I am going.)
* Oui, je pars. (Yes, I am leaving.)
* Oui, tout de suite. (Yes, right away.)
If you are not leaving:
* Non, je reste. (No, I'm staying.)
* Non, pas pour le moment. (No, not right now.)
* Je vais rester un peu. (I'm going to stay a bit.)
If you are unsure:
* Je ne sais pas encore. (I don't know yet.)
* Je dois voir. (I have to see.)
More casual responses:
* Oui, à bientôt. (Yes, see you soon.)
* Non, je vais rester ici. (No, I'm going to stay here.)
It's important to be polite and use a friendly tone when responding to "allez-vous".