I think I read somewhere when you use 3G and you enter a zone where you can get Wifi the console automatically switches to Wifi so that your 3G subscription isn't used for nothing, is it true? if it is, the display isn't very clear about that, 3G SFR is still appearing when I'm near my box, which is misleading
Yes it basically tries to connect to wifi first. When I am out somewhere and it picks up a wifi signal it'll pop up with a list of wifi spots to connect to (though typically random ones I run across in the wild are passworded and thus useless). You just hit the close button on the list of wifi spots and it'll then connect through 3G. If you are at home with a wifi signal that you've already programmed into the Vita and are always connected to it will automatically use that and not even indicate that which it connected to (but rest assured if you have wifi signal and it's programmed into the Vita then it'll use the wifi first). One thing to watch out for: turn off roaming if you are going out of the country. It won't warn you if you are using roaming if you have it checked. One guy kept his checked, used his Vita in Mexico through 3G, and ended up with an 800 dollar bill. Just uncheck roaming in Settings under Network altogether and you'll be free of the worry.