ptboise,
I don't have either rose, but Dortmund is on my list to try.
I checked the dave's garden and helpmefind websites.
Dortmund is listed as zone 4 on both sites.
Dublin Bay was listed as zone 5 on dave's and zone 6 on helpme find.
Looks like Dortmund will be hardier, but if you have a microclimate Dublin might be worth a try.
Barb

Barb - thanks! I was leaning towards Dortmund on the West facing (more exposed) site and your comments have helped confirm that. As always, we shall see - the microclimate in my little valley poses strange problems. Thanks again, Barb.

You are quite welcome. Good luck!

I'm not familiar with 'Dublin Bay,' but 'Dortmund' has been growing at the Idaho Botanical Garden for several years (on an arch in a completely exposed area), so apparently it is thoroughly hardy here in Boise.