Lol, thanks for the advice ratters, but I doubt that a plum that thrives in Tasmania will do well in Idaho, USA. For perspective, my altitude is 4,705 ft (1,434 m) and the current temperature is -2 F (-19 C). We regularly get wind in excess of 25 mph (40 kph) Today I think we reached about 15 F (-10 C) during the warmest part of the day, and that will be quite normal till March or so. On monday we had winds at 55 mph (89 kph), so I'd need something sturdy. I'm jealous of your plums; the wine sounds amazing.
Atvar, I don't know what the plums from the park were, maybe I can call city services and ask them. Some sort of plum apparently does grow here, I just have no idea if they are good for wine. Does the variety affect the quality of the wine strongly, or will any good eating/jam plum make a good wine?