My opinion is your 3.2 GPA shouldn't discourage you, if the programs you'll be applying to are more professionally oriented rather than a stepping stone for the PhD. If that is the case, your internships will be a huge asset, especially if the program includes financial applications of IE/OR tools and methods (relative to your internships).
However, your greater liability for the adcoms will be your questionable quant background. You come from a non-engineering UG, with rather average grades in math (that C in prob/stats might hurt you). If you had the opportunity to take courses from a respected institution in Stochastic Processes and Mathematical Modelling I'd say you'd pretty much make up for it, displaying both determination and good understanding of the science.
GA Tech has a reputation for being too strict with their GPA standards. Don't take my word for it though. If I were you, I'd also cross Oklahoma,Auburn,Clemson and Texas A&M off my list. If you are able to support the tuition on personal funds, you could perhaps aim for a top 10 institution. Good luck!