It all depends if you can stand the heat around here........I sure can't and I love my a/c.....
plus, if you're taking a girl out, are you going to let her sweat her coochie off?
As far as slowing the car down, unless you're going for a full out drag car I don't think you'll notice the difference. Run your car with the a/c off, that way the only thing affecting you is the extra weight of the a/c components.
thats my $.38.....