Eriophora ravilla (Tropical Orb Weaver).
Photo: 06/20/15, noon.

Tropical Orb Weavers can show a great variety of colors and patterns, although many are dull brown. This one features a number of bright pigment spots that create a cross-like pattern. The species is mainly found along the Gulf coast. 
bug guide (this photo):
H. W. Levi (article):