In October, Equality California chose to abandon an attempt to repeal Prop 8 at the ballot because they believed they would lose.

Another group however still intends to give it a shot:

A gay rights group that wants to repeal the state constitutional amendment that stripped same-sex couples in California of the right to get married received clearance Friday to start gathering signatures for a measure that would rescind the gay marriage ban known as Proposition 8.

Los Angeles-based Love Honor Cherish has until May 14 to collect the 807,615 voter signatures required to qualify its initiative for the November 2012 ballot, the secretary of state's office said.

... The repeal initiative submitted by Love Honor Cherish would strike Proposition 8 and state instead "that marriage is between only two persons and shall not be restricted on the basis of race, color, national origin, sex, gender, sexual orientation, or religion," according to a summary prepared by the California Attorney General's office. -- The Mercury News