I am in Florence Italy and relying on my iPad now. This is my strategy.
First, I replaced the iPad simcard with an Italian prepaid card. I am using tre.it. I have 3g with a set price and no AT&T charges. Cards are sold in Europe from other cell phone companies as well. You may be able to order one from the US if you have time. I bought mine in Italy. Second, download maps. This way you can navigate and use your GPS offline. I am using CityMaps2Go. Several options are available at the app store. Third, download city guides. Who carry all those books? Fourth, download audio tours. Rick Steves is a good start. Fourth, sign up for VOIP. I use Truphone. Call home cheaply. To summarize, the iPad is wonderful for a European trip using both 3g and WiFi.