Shortly after writing my original review, the owner messaged me and kindly apologized for the experience I had had and offered my date and I to come back and try them on his dime. The timing never worked out quite right and I had forgotten about his generous offer. My bad!
I just tried their wine again at Devour and spoke to the owner for a little while and he is a great, friendly, knowledgeable man. He was the most enthusiastic of all of the 30-some wineries there and the Summer Rain white was one of the best I had tried the entire day!
I think Su Vino deserves more stars than I originally gave them and I am betting that my experience was more of a one-time fluke than how they typically operate business. I need to go visit their shop in Scottsdale and get some of that delish Summer Rain!!