Before I came to Los Angeles, I had never heard many of these expressions and if I had heard them I would not have had the faintest idea of what they meant. Now I understand them because of my contact with a wide range of Latinos in Los Angeles, but they are not universally understood.



The only universally understood and unmistakable expression for defecation is Laura's suggestion: "¿cuándo hizo caca?" and the only universally understood and unmistakable expression por urination is "¿cuándo hizo pis?" These are universal because they are the words used by every parent with their children. Everything else has the chance to be misunderstood or not understood at all.



Among the rest that were given above, probably the most common are "¿cuándo fue de cuerpo?" and "¿cuándo fue de vientre?" The references to "número 1" and "número 2" are also fairly common euphemisms.



However, if you want universality and clarity, "caca" and "pis" are the words to use, in spite of their not being polite, refined or elegant.



Saludos