I don't know if I would. If everyone I ever knew was in this little world, and they all put so much effort into creating this world for me, then I would feel obligated to stay.
Really? You have to travel, literally, to the ends of your world just to find out what's wrong it, the great unknown that has haunted you for years that has driven you near to the point of madness, only to find out from some voice in the sky, after he tries to drown you, that it was all bullsh!t crafted for the entertainment pleasure of voyeuristic sickos, and you would want to stay?
At some point Christof should have volunteered the truth to Truman, then maybe things would have been different, but, given the circumstances, what reason does Truman have to trust or believe any of it? The voice in the sky could have lied. If Truman turned back, without seeing for himself what was really out there, wouldn't he spend the rest of his life wondering if, perhaps, The Truman Show wasn't part of an even larger deception?
Even if she were welcomed back onto the show, Sylvia might never agree to go there. It would be like a radical activist for PETA voluntarily choosing to accept a job at SeaWorld.