FWIW, Transit on my iPhone, after using it in several large, dense cities (including San Francisco and the Bay Area), only uses up 42.5 MB. So I doubt it would

FWIW, Transit on my iPhone, after using it in several large, dense cities (including San Francisco and the Bay Area), only uses up 42.5 MB. So I doubt it would use very much on your device, especially if you only want to try it out once in your area to see how it works.