Prop 8 is only in CA/for CA.
While religious bigots will vote "yes" for all the wrong reasons (for the sake of being anti-gay), don't let the "gay rights" issue become a red herring: Judaism, Catholicism, Protestantism, Mormonism, Islam, Buddhism, Jainism, Sikhism, etc. all define "marriage" as between men and women. The very concept of "marriage" (a purely religious idea not synonymous with monogamy, simply living with someone forever, OR legal/economical implications) was brought about by some of these people many thousands of years ago.
You gotta ask yourself: Does one really have the right to mess with the ancient, sacred traditions of these people?
A "no" vote just to "stick it to the religious" is just as bad as a "yes" vote to "stick it to the gays."
I just don't like the idea of stealing someone else's idea and forcing them to change it to suit you. At least give them the courtesy of giving it a different name.
I'll vote for gay rights, but also for separation of church and state: religion that isn't governed by the state's own doctrine. I say stop calling it "marriage" in lawbooks altogether. Allow civil unions for all who apply--but leave the religious ceremonies to the religious!