Unintelligent means exactly what it sounds like it means––not intelligent, not smart. Your unintelligent dog might not know his own name, but you love him for his goofy sweetness anyway.
Don't confuse unintelligent with unintelligible. Unintelligible means something that can't be understood. Some doctors have handwriting so messy as to be considered unintelligible, but that doesn't mean they're unintelligent. If your cell phone signal is weak, you might find that what your mom is telling you on the phone becomes unintelligible to you — but that doesn't make you unintelligent.