I'd still say you'd be barely functional as a person; you'd probably have to be looked after in a large city. With a '3', they're only one point above a bright animal. They would act almost purely on instinct; some of the things they'd do might even look intelligent but they would be more the result of chained behavoirs trained into them, like you would a chimpanzee.
They're not retarded like a human with a 30 IQ would be. They'd have some language skills but probably not be able to read without some amazingly gifted instructors; they could recognize some symbols, but that really only puts them on par with most of the illiterate populace. They'd be able to recognize friends, foes, etc; they'd have some short-term and long-term memory, but not a lot and they'd be easily fooled in some tasks. They could certainly be cunning: a wolf can be cunning, and it's significantly stupider than a person with a '3'.
I guess the best way to put it, esp. if the character has an average or above-average wisdom and/or charisma, is that they are remarkably.. uncluttered. Their thinking is very pure and simple. Things are pretty black and white. I am full or I am not. This person is kind to me, or he is not.