The size, shape and leg arrangement as it hangs upside-down in the web, marks this spider as an Argiope, as previously noted.  The big white band on the front of the abdomen suggests A. argentata, but the photo is blurry enough that some of those spiders might be A. trifasciata.  I'd be happy to put it down as Argiope species, in the hope that more, and closer photos of this neat and completely harmless (to humans) spider are forthcoming.

[![Argiope argentata][1]][1]


  [1]: https://i.sstatic.net/F20DW.png