If a majority of the electors voting on the proposition in the City of San Diego and a majority of the electors in the other section specified in Section 90050 vote in favor of the creation and establishment of the district, the board of supervisors shall cause a certified copy of the order declaring the result of the election to be filed in the office of the Secretary of State, from and after which the establishment of the district shall be deemed complete in the City of San Diego and the other section specified in Section 90050.