This worked great for us...
We had the good luck to stumble upon an important fact about one of our houses: if a fan was pointing into the house in the living room, and a fan pointed out of the house in our bedroom, we got a great airflow that managed to cool most of the house. We were very comfortable. It's worth a try with your fans and windows, you might find the magic combination in your house!
Fans are much more cheap to run than air conditioners...we found that out when we started out air-flow thing and got our first electric bill.