From what I've read you can tell if your car has it if it lights up when you hit the ignition.

My car doesn't do that, and its not on the original window sticker either.

Only thing that is suspect is the fact that there is a relay for it under the hood.

Am I safe to assume they just put the relay in every car?

 

^+1, if the light doesnt come on and the sticker does not have that option listed then you probably dont have 4was. Best and guaranteed way to know is to kneel down and look at the rear differential from the back of the car and if you see an actuator/motor type unit attached to the diff pumpkin then you have 4was, if you only see the rear diff pumpkin then you dont have it.

You should be able to tell if you have it or not by just driving too in turns or swift lane changes...