allright.
Algunos de mis compañeros de trabajo se
hablan en español, pero casi siempre lo uso
para probar el tilde en mi teclado
(unnecessary commas). Tomé la materia en la escuela secundaria,
RBF (riéndome bien fuerte)...
The difference between "algunos" and "unos" is very subtle (almost no difference at all), but "unos" is almost never used as a sentence starter.
"Dicen" is used when you have a very specific thing to say, in this case, it would work if you said something like "se dicen frases en español", you are referring to specific phrases. "Hablan" is more like saying "speak".
The commas you used were unnecessary pauses.
"Para" replaces "to"... "por" replaces "for"