One way I'm getting around this issue is to always play the game in windowed mode (from video options). Once you have the window on the right screen, full-screen it with the green button and it works. The game seems to always start in a smaller window this way.
As Mac users, we also have to accept that Mac gamers make a very small % of the user base, and therefore are not as high of a priority. I'm just happy to be able to play this game on my MBP.
