We had a dog that would say "I love you" as plain as day. She could say a number of words and speak in short sentences. Lots of funny stories involving that dog.
She loved to go for rides in the vehicles. After my sister learned that she could say "I wanna go" she used to make the poor dog say "I wanna go" before she would take her for a ride and get her favorite little package of powdered sugar coated doughnuts at the convenience store. Ha.
The best thing was seeing the shocked looks on the faces of people who were skeptical of her ability to "talk". Ha.
Our last dog could say "I love you" and a few other words, but never had the "vocabulary" of the other one...probably because she thought I was a mindreader from the way I anticipated her wants and needs. Ha.