"Sometimes the answer is ""no"". As in this case, you cannot migrate and keep faces and places. You would be lucky not to lose your events, but Picasa and iPhoto use a different system for that.
Bottom line (even though it's not good news): be prepared to make lots of manual corrections and re-enter data if you want to migrate. Don't ditch iPhoto until you are happy with Picasa, or youll end up with 2 half solutions.
According to this article on Google Support, you can choose "Import from iPhoto" from the file menu in Picasa. As dyve suggested, I highly doubt it will preserve Faces and Places, but I think it might preserve events (although don't take my word for it).
