If you want to play them via iPhoto you're going to have to use something like ClipWrap to change the wrapper (without transcoding) from MTS to MOV, before import into iPhoto.
(I can't vouch for this personally, so test first to make sure it does actually work as expected.)
Clipwrap looks about right, even if 50$ is expensive for what I would expect Aplle software to do out of the box!