HOLT - Gov. Arnold Schwarzenegger said Saturday he is very optimistic about reaching agreement on a law offering driver's licenses for undocumented immigrants and denied he is insisting the licenses carry a mark that flags the holders' illegal status. But the Republican governor said such a mark, which license supporters have decried as a scarlet letter that would lead to discrimination and abuse, would be the next best thing if he and lawmakers can't come up with other ways to meet security concerns, principally a way to verify the license applicant's identity. "If they cannot satisfy all of the security...