Not all events have reliable WiFi, so I want to know if the Marketo Events app for the iPad will work without WiFi. And if it does, can I just sync the leads when I get to WiFi?
You can synchronize you ipad before the event when you are in the office and synchronize it after the event when you are back.
But, for additional reliability and flexibility, being able to stay permanently online is better. We use an Ipad with a sim card and a 3G/4G connection.