Please be sure to check out the Phase I Food List in the FAQ Section. There are several differences from the foodlists in the book and yogurt is one of them.
In Phase 2, when you can have artificially sweetened/flavored yogurt, you may find, like some of us did, that the ingredients are kind of scary! They add all sorts of things to the yogurt, like gelatin ( ), and so some of us use plain yogurt (I prefer Stonyfield Farms organic) and add SF jam, SF syrup, or other things to sweeten it. I love plain yogurt, SF raspberry jam, a little splenda and cinnamon, and a tablespoon or two of wheat germ. YUM!
I'd stick with plain. The flavored stuff just has too many chemicals and other added things in there. It's so easy to add your own flavorings the other stuff is just not worth it. Just my 2 cents!