I've grown Tuttti Frutti and a couple other that I can't think of right now...I grow them from seed. They come back each year, but not always. I like the look of them, kind of similiar to salvia, but more delicate. Hummingbirds love agastache.

From what I just saw online, they prefer well-drained soil and are perennial. For Dallas, that tells me they need to be in a raised bed or an uphill area that's been well-amended. If you can do that, I'd definitely try it.

That said, I just check Lady Bird Johnson's Wildflower Center and found that only one cultivar is native to Texas and that's only the Trans-Pecos Region. So, the others may not tolerate our summers well. Could still be worth a try, if only as an annual.

Here is a link that might be useful: Native Plant Database