Gallup poll: Hispanics 2-to-1 for Democrats both before and after Arizona immigration law
Hispanic voters nationwide haven't shifted their congressional voting preferences since the signing of Arizona's new immigration law on April 23. Their preference for the Democratic candidate over the Republican candidate, 61% to 32%, in April 23 to June 8 interviewing almost identically matches the 60% to 32% margin recorded between March 1 and April 22. White voters and black voters also haven't changed their voting intentions.
Bear in mind, of course, that this was a nationwide poll and wasn't of, say, Mexican-Americans in Arizona or Southern California. However, it does contradict specific propaganda efforts like CNN's "Arizona Democrats say immigration law energizes Latinos" (link) as well as the more general predictions of electoral doom unless politicians basically turn immigration policy over to one ethnicity.