Ni hao Natalia!
I too agree with Dilce and Forvill.
In Portugal, nowadays, is not so frequent to use the words 'garoto' and 'garota', but when used they are meant to refer to someone from young childhood to the start of adolescency (maybe from 5 to 10/12 years-old). In Brasil I know the words are applied to older ages...
'Menino' and 'menina' are words applied to young children, from birth to the start of adolescency, but we use more often the word 'criança' (sounds like 'crianssa' and is the equivalent to 'child' in english). In Portugal we consider that someone is a child ('criança') until he/she is 16 years-old (although many get offended to be called a child by that age, so I advise you to address to someone younger with 'criança' only until the age of 12/13 years-old - they get less offended :).
We use the term 'menina' also to address politely to a young woman who hasn't married yet. It's the equivalent to the english word 'miss'. The term 'menino' as means of addressing to a young boy in the same condition is less frequent, but sometimes is also used.
'Homem' and 'mulher' are terms used to refer people who entered the adulthood. There is no established minimum age for it, but we use it more often with people near the age of 30 years-old.
I hope I have helped.
All the best
PS: just a curiosity - we also have a drink named 'garoto'. Is an expresso coffee with half the cup filled with milk.