The following table contains data on all 2009 surveys I could find that break out support for gay marriage among Hispanic respondents. This includes one national survey, one California survey, and three New York Surveys. In addition, I include two prominent surveys from 2008: the
The Prop 8 exit poll reported that 47 percent of Hispanics voted 'no' on Proposition 8 (indicating their support for gay marriage) as opposed to 51 percent of whites; the difference is not statistically significant given the sample size. Each of the other surveys indicate that Hispanics support gay marriage at almost exactly the same rates as non-Hispanic whites, except for a recent Quinnipiac national poll, which actually has them supporting gay marriage at significantly higher rate than whites.
If we aggregate the eight polls and weight by sample size, we find essentially no difference in support for gay marriage between Hispanic and white voters. (Please note that the 47 percent figure you see should not be read to mean that this is the number of Hispanics who support gay marriage nationwide, since the average includes a disproportionate number of respondents from New York and California, two very liberal states -- the relative support for gay marriage is all we're examining here).
Now, it can be argued that because Hispanics are more liberal than whites on most other issues, gay marriage is still a relatively good way for the GOP to garner support with that group; some scholarly research has suggested, for instance, that "moral values" issues were an important source of Hispanic votes for George W. Bush, who performed relatively well among the demographic in 2004.
Further evidence from the General Social Survey, however, calls that claim into question. Although the relevant sample sizes are somewhat small, their polling in 2006 and 2008 suggested that about half of Hispanics who were opposed to gay marriage nevertheless voted for John Kerry; the comparable fraction among non-Hispanic (mostly white) voters was only about one-third. Hispanic votes appear to be less sensitive to this issue than are white ones.
Black voters, on the other hand, do indeed appear to be quite strongly opposed to gay marriage -- but they also, of course, vote overwhelmingly Democratic.