DOGGER - hi, thanks for posting back to let us know. As for your attic ventilation query, there's been some good recent discussions in the Roofing & Siding area of this BBS. You should look there and see what's been discussed.
The very quick answer - the fan is only 1 type of ventilation and the attic area should have 2 types. The types used have to let a certain amount of air flow through to be effective. Some types can work against each other, e.g., a gable fan and roof ridge vents...the methods used need to work together, e.g., soffit vents and a gable fan.
Unless you've got an AC duct run into your attic area, or a broken duct letting cold air into the attic, the attic temp shouldn't affect your AC bill. You may need to do (or have the local electric company do) an energy efficiency exam of your house, where they look for window drafts, etc., that would let the cold air escape/hot air in, which would push up the bill. Also, your system may need a Freon recharge or it may have clogged filters, forcing the system to work harder. I just went through having my indoor air handler replaced due to multiple coil leaks. The installer found and removed one of those mohair permanent filters from the new unit because most people forget about them and they clog up over time. I have the standard fiberglas disposable filters on my air return ducts, which I replace the first Saturday of every month otherwise.
I hope this helps some - it's not my area of expertise but I read what the experts post here. Good luck! Jim D/West Point, VA