I vote for the bike PS (and I'll read, if you don't mind waiting a few days). Do you already have a diversity statement? That's where mission work and learning a new language could go. Not necessarily to show that you're different from other applicants because you did a mission, but because the skills you gained while doing the work make you more likely to speak up in class/view things from a different perspective/take on new projects no matter how hard they seem initially. I think put together, these two statements could really show the adcoms both your background and your passions.