Mine doesn't have any alarm that I know of. Maybe on the SLT's?
I'm Not sure about the SLE! But I have to say that I didn't even realize that we had an alarm until I read the manuel. Give this a shot, Try pushing your remote key fob lock button 2 times and if the horn sounds once you have an alarm. I may add an additional system to my Acadia. Not sure what it's called but on my old vehicle we had glass break (so even if someone banged into the Acadia the Alarm would sound).
Let us know if the SLE has it.
I am pretty sure that all the models of the Acadia have the Theft Deterrent System - read pages 118 - 122 in the manual to learn more about the system - it is basically the horn will sound and lights flash if someone opens the door without deactivating the system with the key fob or turning the key manually in the door - so if someone broke your window and reached in and unlocked your door the horns will beep and light flash. We also have the Passkey system which is a special chip built inside of our keys - the vehicle reads the chip - if it matches then the vehicle will start - if no chip is detected the vehicle will not start.