In your shoes, I'd probably choose to take more undergrad level science classes through a DIY ("do it yourself") postbacc to raise the GPA. With you working full time, taking 15 credit hours per semester probably isn't possible but taking fewer and getting straight As would probably help more than teaching abroad except if the teaching abroad had more of a service component such as Peace Corp or Fulbright.
Note that taking masters courses or getting a masters degree won't raise your undergraduate GPA. Postbacc undergrad courses are included in computing your overall undergrad GPA.
However, I'm not an ad comm. wysdoc and catalystik are TX ad coms. They might respond if you tag them.