You have to know the spoken language first in order to understand Cued Speech. It's not a language but rather a mode of spoken language - just as the printed word is a mode of the spoken language. If you have a limited knowledge of a certain spoken language, cued speech would be meaningless to you. If I relearned cued speech and it's cued in English, it'd be understandable to me. However if Spanish is being cued to me, it will have no meaning to me.
If I were to rely only on spoken Spanish around me, I would have limited access to spoken Spanish and I may not be able to figure out how to write a proper sentence in Spanish. Spoken languages have to be taught to deaf children as we can't pick it up just by hearing it. Few use cued speech. I'd have a much easier time learning Mexican Sign as it's much more accessable to me than spoken language despite my implant.
Language delays is very common in deaf children if they have limited access to the language around them and it's hard to overcome.
