Well, this could get spoilerish for our American colleagues
Balter & company aren't on Caprica. - They got shot down over Kobol. - Boomer & Crashdown found Kobol and reported back. When the Fleet sent in a survey team, the found the cylons had since jumped in.. Three Raptors were sent. One was destroyed, one escaped and the one with Balter on crashed.
Starbuck is on Caprica because the Pres sent her back to get something which would help point them in the direction of Earth once they got to Kobol