There are numerous salt-tolerant Florida native wildflowers suitable for the beach:

• Seaside goldenrod (Solidago sempervirens)
• Frostweed (Verbesina virginica)
• Blanket Flower (Gaillardia pulchella)
• Beach Sunflower (Helianthus debilis)
• Tropical sage (Salvia coccinea)
• Carolina wild petunia (Ruellia caroliniensis)
• Dotted horsemint (Monarda punctata)
• Sky blue lupine (Lupinus diffusa)
• Pineland heliotrope (Heliotropium polyphyllum),

These are just a few of the possible choices. 

Additional Resource 

http://www.fnps.org/pages/plants/landscape_plants.php

http://www.floridayards.org/fyplants/index.php