The use of Spanish has really ramped up in the past few years.
I've never been an "English only" sort of person, but the level of use is beginning to bother me. Spanish newspapers and TV? No big deal. You could be here for a long time, know English and still prefer TV in your native language, and heck, my great-grandparents read The Forward, not the Times. Or even stores or products using Spanish to grab Spanish speaking customers.
However, when Spanish and English have equal prominence on signs and packages, and I have to look for the English, my patience starts going. When I can't find anyone in the produce department who speaks English well enough to understand my problem, that's an issue.
The final straw for me was when I was in the Gap last week and the ad for new sales associates was in English and Spanish. Honestly? If you can't read or understand English well enough to apply for a job, you have no business being in a customer facing role in an area that's at least 80% Anglophone if not more (and probably higher amongst the Gap's clientele).
I don't think we should force people to speak English, but I think a common language is generally a good thing. I know that contrary to the "my grandparents came here and they had to learn English!" story, immigrants have never immediately learned English. Spanish seems to have enough of a bloc to persist, though, if speakers choose to--and I can see a real backlash happening.