I modified the rules.txt for the AI to go straight to monarchy, stop irrigating right off the bat and build cities instead. One thing i noticed that if the AI starts on a river, it will irrigate all squares no matter what.
replace your rules.txt with this one and give it a shot in single player. http://216.232.0.147/rules.txt
replace your rules.txt with this one and give it a shot in single player. http://216.232.0.147/rules.txt