yes, that's one of the problems with insects, sometimes differences betwen species are very subtle, other times the same specie can have many different colorations and shapes (polimorphism)
Good guess, Ashish. But if you look at the shield above the head you may notive that the black parts are separated in Mexicana in Cingulata not. And there are no white parts next to the body in Cingulata. In addition Cingulata seems to be a South American species. Membracis mexicana is safe in my eyes.
This one is from Colombia:
http://www.flickr.com/photos/roboelman/6154000074/in/set-72157627686046288
Also from Colombia, but not Mexicana:
http://www.flickr.com/photos/roboelman/6154000704/
http://robertoelman.photoshelter.com/image/I0000TNxzox3m00g
And this one from Arthur from Ecuador with a wrong ID...
http://www.flickr.com/photos/artour_a/4369987103/in/set-72157612250897407
It is also Phyllotropis cingulata not Membracis mexicana.
Is it in Genus..Phyllotropis..?
http://www.google.co.in/search?q=Phyllotropis+cingulata&hl=en&prmd=imvns&source=lnms&tbm=isch&ei=_SPLT6GAAozorQf3s427Dg&sa=X&oi=mode_link&ct=mode&cd=2&ved=0CEMQ_AUoAQ&biw=1280&bih=713
http://globalspecies.org/ntaxa/2366751
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