I just got an Ipad. I already have an Iphone and a data plan. Do I have to get a new data plan?

If you have a Mobile Share Plan, No, you can simply add your iPad to that. If not, Yes, you will need to get a data plan specifically for your iPad. Currently there are three Tablet data plans available to choose from; 250MB/$14.99, 3GB/$30.00, and 5GB/$50.00 a month... More on tablet data plans can be found here: http://www.att.com/shop/wireless/plans-new.html#fbid=YdHjUD55RU8. 

Hope this helps. 🙂