I think it will be very difficult to grow any rose with out supplemental water unless you have regular rain. Concerning Mermaid, it is a large flowered voracious climber with heavily thorned brittle stems. Given its head it is a beautiful well scented rose. I cannot tell you about its desease resistance. It is a hybrid tea.

Mermaid is classified as a Hybrid Bracteata. I grow it near Birmingham, Alabama and it does really well in our heat, but it does need supplemental water.Once mature, I suspect that it won't, given the size that it will eventually grow to.

It will get real big, and once established will likely do well with neglect. However, it is one of the last roses I would want to have to weed around, etc., so be careful with it in that location. I personally wouldn't use it, but if you rarely go back there, then it should work. I would tend to think of natives for that type of area. For roses, I might be tempted to put in the one of the Banksiae varieties, although they are once blooming. Also, deer don't like to eat the Banksiae as much. If you want a bush variety, then I would go with one of the chinas like Mutabilis, C Superieur, or a tea like BR Cant.