Hmmm. I'm zone 9b/10a, and they do fine for me... but I'm near the coast which tempers me a bit. You might try the more common, old fashioned ones? Though right now, I'm loving 'peach melba'...it's pale yellow with red markings in the throat. Not quite sure how they came up with 'peach' for the name, but it's my favorite I think!

Amanda 'romando'

They will slow down flowering as the summer days and nights get hotter and hotter. They'll last longer if you provide some shade in the hottest part of the afternoon. Get them started early for a longer flowering period.

Thank you so much for your responses. I think I am going to try them.