Since there is no jailbreak out yet and I can't use 3G unrestrictor, is there any way to watch high quality YouTube videos on 3G without jailbreaking?
Yep, a while back I replaced the default YouTube App with a link to m.youtube.com and have been very happy with it. Not only the fact that you can use the HQ button, but you also get any updates that they decide to push out and don't have to wait for an iOS update to get them.