Actually, most Jews spoke Greek
and Aramaic. They spoke Koyne Greek (translates to 'Common Greek'), which is why the gospels were originally written in Greek--so that the people could read them. There wouldn't be much point passing around scrolls when you're in the catacomb
s if nobody can read it.
The reason it was in Aramaic
was probably because that's what most Jews spoke primarily. They could
speak Greek, but it was more of a second language.
Just to try to clarify that point.