Not everything in the book is true such as demigods cant use technology because we can as monsters seem to leave us alone and don't attack us. This could be because we are not powerful enough for them to care about us. Percy Jackson was a powerful demigod he had already used his powers as child without realising which made it so easier for monsters to find him you don't have anything to worry about our powers are different to like in the books we cant control them as easily in the real world. We don't know where camp half-blood is and probably never will it might not even exist but it doesn't matter because it isnt likely monsters are going to come after us so dont worry and im sure if we were attacked a saytr would come and find us because saytrs do exist we havent seen any but there is proof if you look hard enough. We dont even know if Percy Jackson himself was real but he could have been and Rick Riordan could be a demigod but we may never know. The gods of olympus are real i dont know if they do live on the empire state building hidden from mortal eyes but they could be. There are no titans they are locked up in different places so anyone claiming to be a child of a titan is a fake.