Can I sign up and use for a month or two, cancel at anytime if we wish? If so, what is the monthly charge?

Yes, you can upgrade to any of the paid plans and cancel it anytime you wish. You can check all the plans on our pricing page here https://www.jotform.com/pricing/. 

We also have an ongoing end of year sale discount, 50% off when you upgrade to yearly or bi-yearly plans.