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 catacombs 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.