Green cheeks are not noted for talking. You have a very precocious baby there Just talk to him all the time. They love animated ,excited voices. It is not unusual for conures to talk while still being hand fed.
Incidentally your bird is a bit young to be fully weaned.(although it's possible.) Make sure he is eating properly to avoid a lot of problems later.
Hey my baby green cheek I've had for 5 days now and when he was nipping at me I said "ouch" loudly to kinda teach him that it was wrong and he actually mimicked it! It wasn't too clear but I could hear it!
Is this abnormal because I've heard that conures talk at around a year old.