On February 5, Capitol Weekly/Probolsky Research Poll released a poll on whether Californians would vote for a “top-two” primary system. The idea received support from 49% of the voters, with 35% opposed and the rest undecided. See here for the details.
The specific “top-two” proposal that may appear on a future California ballot is limited to state office, not Congress. The idea is pending in the legislature as ACA 6, a proposed state constitutional amendment sponsored by Assemblymember Charles Calderon. Because it changes the California Constitution, even if the legislature passes it, it would then go to a vote of the people. Or, it could be a constitutional initiative.