You are not allowed to choose your Race before joinning the game.
First you have to Join Quick Game => The Game Search System Finds 5 Players => Players are in the Waiting Lobby => Here the 5 of them can vote, who wants to be the Predator =>Predator is chosen, FireTeam is selected => game is starting!
In case that all of the players chose themselves as the Predator than the game system will select the first player who voted himself as the Predator. Same rule is applied if some players have 2 votes each, the player that made first the 2 votes wins.
If that is not the case than the player with the most votes wins.
What do you think?