Every bird is different! I don't know anything about the talking capabilities of a Black Cap Conure, that might be something that you'll want to look into or maybe another person on this forum can help with that. You should know that no bird is guaranteed to talk. Even African Greys that are known to be excellent talkers will sometimes never learn to talk. Some birds that aren't known to be very good talkers can develope quite the vocabulary. Never get a bird if you're solely wanting a bird that talks. Even if you get a mature bird that talks there's no guarantee that it will talk when you own it.
My Amazon picked up 'Hello' around 3-6 months of age. When he's learning new words they're usually nothing like the actual words. He will mumble things to himself that eventually become clear with practice. He has picked up words that I didn't want him to, and there's other words that I've been repeating since the day I got him that he hasn't picked up.
Based on my personal experience, birds tend to pick up on words that are spoken with emotion or when they're in a heightened state of emotion. Such as if you stub your toe and yell 'ow' it's quite likely the bird will add that word to their vocabulary. Or if you say hello every time you come home or enter your bird's room. If they've been lonely and waiting to see you all day and you say an excited 'hello!' when you enter the room they'll be more likely to start saying it. Repetition and consistancy also helps. Always say step up when you want your bird to step up, say hello when you see him, say 'wanna come out', and repeat the name of an item that you're giving them.
Just remember that some birds learn more slowly than others, some birds do not speak clearly, some birds never speak at all. Just love your bird for the individual that it is .