I'm not sure about the 3G and 2.0, but on my iPhone with 1.1.4, I can go to "Settings > General > International > Keyboards" and add a keyboard. I added the French Canadian one here. It allows me to switch keyboards while typing. The French Canadian keyboard doesn't trigger any auto-correction and has the same layout as the US one, only difference is that space is labeled "espace" and return is labeled "entrée".