Assembly Speaker and one-time Pomona immigrant advocate Fabian Núñez is heading into a defining year in his young political career, saying he is prepared to get things done. But critics say the Los Angeles Democrat is only prepared to be an "obstructionist." In a legislative session that was overshadowed by partisan bickering surrounding November's special election, the perception that Núñez can't or won't negotiate was reinforced by his outspoken criticism of Gov. Arnold Schwarzenegger after election day. Unlike the speaker's Senate counterpart, state Sen. Don Perata, D-Oakland, who was more conciliatory, Núñez had said, "It can't be just one of...