I'm interested in this as well. Best bet is to try the fruit festival and ask around.

I planted a Waneta 3 years ago. It was purchased from Costco. Last year it set one fruit and it tasted like Pambina. Sweet, juicy but the skin is tart. Last year I planted a Toka for cross pollination. Unfortunately, they did not flower at the same time this spring. It did not set any fruits this year.

Many years ago I planted Superior, Toka and Pipestone plums. They all fruited and had beautiful fruit, but the only one that was delicious was the Pipestone. I have seen other reports that the flavor is bland. The Pipestone is the only one around today (after 40 years).