cheaper to run all fans or the main air conditioner on the house.?

The best answer I can give you is the way we cool our house. We have an air conditioner in the main room's that we use. By having window air conditioner's we can just run it in whichever room we are in at the time. Central air you have to cool the whole house and it run's alot more than the other kind. We also sometime's run the ceiling fan to help circulate the air throughout the room. Believe it or not our power bill is less in the summer than in the winter. We live in Ga. so the temp's are very HOT here too. Try it and see if this method work's for you and stay cool and comfortable all summer!

The ceiling fans use less electricity, so use them until you "need" the extra cooling power of the air conditioner.

Yes, with the fan setting, only the fan will run. A fan motor uses only a fraction of the energy that a compressor uses.