With 2 INT you can get a unique "ICE CREAM!" dialogue option in REPCONN.
Also, you'll get a discount for the intelligence implant.
Low INT dialogue is fairly limited as a whole, though.
Does it need to be at 2? Ive been through most of goodsprings at 3 and havent seen any difference at all. Thought SOMEONE, even the Doc, should have said something.... You think at 3 its too high? I think that was the limit for Fallout 1 and 2.