Look for this code line in any profile:
<GameParams numGames="-1" isPrivate="True" resumeFromSave="False" act="OpenWorld"/>
It should be there in any profile that makes a game those are the settings that the bot will use. If you change isPrivate="True" to isPrivate="False" the bot will host a public game not join.
Joining is a bit diff but I wont bother posing it as that alone should give you enough to have public games. But I wont advise you to do it as said above its a good way to get banned.