You Certainly can. Acutally, the best time to plant wildflowers are in the fall before the rains come in to get the seed properly set for a spring bloom. thank you for your question.
I would plant a hummingbird mix instead. These plants are specifically designed to grow in the Texas environment and there are other, better seed mixes for the Florida area.
I would say it is deer resistant as much as any other flower is. Deer like to eat almost anything and i don't believe these flowers will dissuade them very much. Plant them anyway, they look so beautiful.
You can but, especially in Texas, it will require a lot of water to get it going. best to wait until after the heat breaks in August to plant and then you will be ready for the rains and beautiful flowers next year!