The lesson is indeed evidently a simple one: should one need to understand a new place, the first place to look is the stomach. This in itself is a rather abstract notion, and should be treated as such; the eating habits are the important aspect, what diners ingest, where they do so and why. Literal observation of stomachs is a practice best left to the trained medical practitioner.
The querulous observer might posit the notion that dining from the street is a bad idea. That it is a wholly unhealthy endeavour. A breeding ground for germs and general dissonance. This is a viewpoint which may well be apt in some cases, but broadly the opposite tends to be demonstrably true; eating street food induces in its subjects the kind of excitement and palpable yearning afforded only by the dawning of some new, hitherto unexplored, experience.
How so? Stimulation and interaction seem to be the key. This is as good a time as any to observe the comings and goings of the surrounding vicinity: how people get around; what their working hours are; the minutiae of their daily existence; the nature of their interplay. The form with money and language is useful; here it is made clear the acceptable forms of currency: an unrealistically large note, for example, may breed momentary consternation in the proprietor. Polyglots, or varying shades thereof, will be afforded the opportunity to acquire the practice so useful to their talents: the speed, depth and practical applications of the local vernacular will become so much more transparent when ascertained directly.
The surrounding hubbub offers a strong indication of the prominent social mores and implicit understandings; is space something to be respected or shared? Are strangers welcomed, ignored or treated with indifference? In taking the time to comprehend the subtle nuances of life, the lesson is indeed evidently a simple one: should one need to understand a new place, the first place to look is the stomach.