Not a winery tip, but well worth it for the visitor. A friend of mine took me to a favourite pub of hers on a work trip to Adelaide recently. The Kings Head Hotel on King William St, Adelaide CBD specialises in SA beer, wine and food. The folks behind the bar will let you taste what's on tap before you commit too, which is nice.
Use the "I'm from out of town and don't have a clue" routine. And do purchase a glass of Maxwell's "Silver Hammer" Shiraz!
Cheers,
Jason