Dan, When the DA roses became trendy here (in the '80's) I tried many of them. Back then, they said to palnt them in groups of 3 or 5 to create fuller, bigger plants. That doesn't seem to be the case anymore, however.
The majority of them just didn't do well in my Zone10a climate. They got every disease in the book, produced very few blooms, and the ones that did bloom fried in the summer heat and humidity we get.
As Neal stated above, the thorniness varies from cultivar to cultivar.
The only 3 DA's I have now are Wenlock, Pat Austin, and Mary Rose. For me, these 3 do very well here. I let them grow into climbers, not just bushes. They're no "thornier' than any of my other roses, just "average" I would say. I bought them pre-grown in 5g containers...so within 2 years they were producing a good amount of blooms and I like them very much.
It seems to me that most of the Austins do much better where summers are cool and not overly hot and humid.
