Not very intuitive, but it worked. Would be nice if there was an auto switch between Wifi and Verizon 3G.
There is done automatically or should be, which is the case with the GSM iPhone and should be no different with the CDMA iPhone.
The iPhone is designed to connect to the fastest internet connection available at the time. With wi-fi and 3G network access turned on, when returning within range of an available wi-fi network your iPhone has access to and has connected with previously, your iPhone will connect to the wi-fi network automatically. When leaving the range of an available wi-fi network your iPhone has access to and has been connected with, your CDMA iPhone will switch to Verizon's 3G network automatically if Verizon's 3G network is available at the time. If not, the iPhone will be connected to whatever is the next slowest internet connection via Verizon's CDMA network.
This is done automatically and seamlessly with the iPhone - switching between the fastest internet connection at the time - at least with the GSM iPhone. I've never had a problem with this including with the original iPhone which is not a 3G network compatible iPhone - switched to AT&T's EDGE or GPRS network from wi-fi depending on what was available at the time, and with an iPhone 3G and now with an iPhone 4. There should be nothing special that needs to be done. Should be automatic and seamless. If not, there is a problem with the iPhone.