I live in Houston and almost all of my driving is freeway driving. It's too hot and/or I enjoy not having air smash into my face at 70 mph or hear a roaring in my ear that sounds like I'm at the runway at IAH. Windows down in my ride about .1% of the time. AC the rest.
They were perfect for smoking too. The smoke would just fly out the window as soon as you blew it. (please, no "that's what she said" posts...)
In Houston I use ac. Out here in the hill country(30% humidity), I roll down the windows under 85 degrees.
A/C unless i'm about to run out of gas, then I turn off the a/c and still leave the windows up until I get to the gas station because it's usually hot as heck outside