Yes, since her family is actually from Puerto Rico, it would make sense that she grew up in a household where Spanish was the main language. I think for people that don't come from a bilingual home is a difficult concept to wrap their heads around, but it is very normal for people who either were young immigrants or first generation Americans. For example, since I speak fluent English people just assume that's the only language I speak, or the main language I use day to day. We haven't seen much of Cece's life outside of her work environment, but is very possible that Spanish is her first language, in fact since they are actually from PR is almost a sure thing that it is.