Any bird species has the potential to be tamed at any point in their life cycle, it's just a matter of the individual in question, and the difficulty... on the difficulty scale, you're talking about a juvenile bird, and that's hands down the best and easiest time to tame. Yes, a bird that hasn't been socialized yet is going to be more difficult than a bird hand-fed as a baby, but for reasons wrench13 mentioned, it's often preferable to get a parrot raised by parents with a clutch of siblings. I certainly don't think you should rule it out!
Just remember that this parrotlet is a bird, not a person, and this applies even moreso because they were raised by birds... this baby has no confusion about what they are compared to you, a predator animal! So you need to respect boundaries above all. Never force interaction in a way that makes the bird uncomfortable, and always offer positive reinforcement treats when the bird is with you and choosing to interact. Bird trust is hard earned and easily lost.