We are never told directly but a boy may take a walkabout from the age of twelve upwards. And I think its clear from the context of the story he is clearly under twenty.
You don't you are too young at 12 to know your sexuality so leave it 2yrs or so then have a go -actually it is fine and you know at any age,just usaully over 11or12,not you DONT know like that idiot...