The best way to debug on iOS devices is to use XCode's Organizer with your device plugged in via the USB port. On the left hand panel of Organizer, there will be a block for each device that XCode knows about. You may have to click on a button "Use device for debugging" or something similar so XCode can gather all the information it needs.
Once done, then you can use XCode to install the app to the device (you don't need to make an .ipa file, just copy the app to the device via Organizer). In that panel on the left, there is a link for "Console Log", click that and you can your print statements and other errors issued by Corona SDK.
Rob