Everyone it hostile until you send peace treaties.  You can make everyone allies at the start by setting everyone as members of the same team, but then the AI will probably not break off the treaties, and you also have to wait 1 min 30 sec before attacking when either you or the other player go to war.  Personally I would not suggest doing this because otherwise you will probably not learn very well how to play, and the game might not let you.  I know that when allied victory is off or after achieving an allied victory and choosing to continue playing the AI will break all treaties immediately.  Im not sure, but I think that either you would auto-win by doing this, or everyone would break off all treaties right away, defeating the purpose, but it could work.  I have never tried it myself.