Childrens Hospital Los Angeles has an ambitious vision for its new building, and some of the $548 million project is being funded through borrowing that California voters approved in 2004 to help expand and update the state's 13 public and private children's hospitals. But all the hospitals say they need more, and they are returning to the ballot Nov. 4 with Proposition 3. The proposition asks voters to borrow $980 million on top of the $750 million they approved four years ago.