I had my engine belt replaced not too long ago. Would it be the ac belt or a pulley that is making the car squeal like a damn pig when it's cold out?

 

the belt has probably stretched since it was installed, causing it to squeal until the pulleys warm up. pop the hood and see if the belts deflect too much when you push down on them (use the attached sheets from the service manual for reference). that's likely the culprit.

 

^ that sometimes happen after replacing belt. Just need a little adjusting and it should be fine happened to me after replacing mine