Hello,
There isn't any reason why you couldn't. The main issue is whether or not there are drivers to support using the screens with the Mac.
For example, a quick search turned-up this company:
http://www.elotouch.com/
They support Macs, and OS X. They do appear to be in 'beta' stages for drivers for use with the newer Intel Macs though. So, you could contact them about access to their beta drivers or an estimated date of completion on those drivers.
They discuss that here:
http://www.elotouch.com/Support/Downloads/dnld.asp
Scroll down to Mac Intel drivers.
Otherwise, it should work. And, appears to have supported drivers for the PowerPC Macs. So, it's probably just a matter of requesting beta drivers for Intel Macs.
But, you can definitely use Touch-Screen monitors with the Macs. You just need to find one that comes with OS X drivers and will work with the model of Mac you intend to buy.
I hope this helps.
Let us know if you have other questions.
P.S., if you'd like, go ahead and click the 'Helpful' or 'Solved' buttons on any of the posts / replies above if you feel they were helpful or adequately answered your question.