You will save energy from turning down fan speed on both AC system and regular fans, but here is the kicker, most AC systems will always run the compressor all the time full cycle duty during the on phase untill the temp of the house is low enough according to the T-stat setting to turn it off so running the fan at lower speed pushes less saturated air thru the accumulator thus possiblly increasing run time and energy use.
New state of the art AC systems uses a varible duty cycle compressor drivers and automatic fan settings that according the Energy Star and Honeywell will save money. Most low end AC systems sub 3-4 thousand dollars (USD) don't have these features, but are still Star certified.
If you run the AC fan lower so should the compressor unfortunatly not all AC systems discretely control the compressor.
From your aspect using AC less will save money, but it is a term of comfort. If you are comfortable at 74, diseased slightly by 78 then set it for 78 to save money.
Another thing about setting high temps is the compressor will work harder the higher the inside temp is because simply there is more heat to transfer and most likely more humidity this loads the freon and makes it harder to pump in the suspension carrier liquid> higher pressure.
If you let the house sit for a day (24 hours) without AC and then turn it on you will burn up 2 days worth of energy (4 or 5 dollars) of running at a constant temp to bring it down to 76ish. Run the AC more at night when temps are somewhat lower, less than at mid-day.