When Verizon goes to the LTE (4G) network you will be able to do both at the same time. They are supposed to be rolling out the new network soon,but it will take some time....depending on your location. Also browsing the web will be much faster than 3G, or even Wifi.
Yeah you can use Wi-Fi and 3G together, they just switch back and forth when you wanna make or receive a phone call. I stay on Wi-Fi for everything because it's faster than 3G in my opinion. dancedroid