2011 GT lowering springs and camber plates
 

Are there springs out there that will give about 1.5" drop for a 2011 without the need to install camber plates?

Its not a matter of spring brand that will determine if you need camber plates, its the amount of drop that affects the alignment. That said, 1.5" is kind of on the border. If you're going more than an inch I'd recommend camber plates. If you're going to modify your new $30,000 car, do it right the first time. If you can't afford to do both springs and camber plates, save a little bit until you can afford the plates as well as new shocks and struts.