The Pechanga Band of Mission Indians and the Morongo Band of Mission Indians, two tribes that are the target of proposed ballot initiatives to limit casino gambling, filed lawsuits Wednesday to block the referenda. The lawsuits allege that the backers of the initiatives did not have signatures supporting the measures certified on time by the state. Pechanga, Morongo and two other tribes signed new agreements with Gov. Arnold Schwarzenegger allowing them to increase the number of slot machines in their casinos.