You know when you play with AI. Most of the time the Zerg stop advancing when they reach to Tier 2 base. They rarely go everything.
Blizzard promised the implementation of an special AI API called BWAPI that might allow what you are looking for, yet, no update on the matter has been done for over a year, thought that is a direct promise from a Blizzard Developer and it must be taken as such.
Zerg Ai is only good at beginning to rush and for lurkers mass hydra allin.
Personally i think Terran ai is the best. THough protoss Ai is the strongest most times and has the best builds. But i have notocied that often Terran ai goes hunt for your overs and has a quite strong marinemedics firebat push. But after a certain level they are just garbage really. Only multiple ai are nice to pracise for certain things or give a certain challenge.