i say use it as an opportunity to be the 'irresistible asshole'! just say oh yea loads but say it playfully so your not SPAM anything and its kind of a neg at the same time.

Wouldnt that give her the impression that you are kind of a player though?

The perfect answer should be vague challenger her to WORK for your exclusivity.. but don't allow her to lead the conversation.. you must change topics upon answering..

I just got asked this question and my response was:

I more enjoy & prefer getting to know interesting people right now, but certainly open to dating the right woman comes along... by the way I was thinking of getting a puppy, do you have or like pets?

From what I recall the last couple times I was asked this I lent in a little closer and said slowly with a fairly serious tone "Why do you ask?" because let's be fair, there's usually going to be only one reason they're asking. Now they might then shrug it off/laugh it off as it just being a general question like "what do you do?" etc, but if they also respond with a fairly serious tone (also watch out for IOI's at this point, if she's interested she'll be flinging them like a monkey flings it's poop) then I say just go for broke and lean in, you know situationally permitting (bit awkward if you do it on a bus for example). I think this way can cut allot of BS out.

I can see argument for some of the other suggestions people have put down but this has pretty much always worked for me.