Personally, I embrace the growth of Spanish throughout the US, but like consuelo, I've spent a lot of time in Latin America and speak Spanish. The San Francisco area has a huge Hispanic population, and when I go to the neighborhoods that are pretty purely Mexican or otherwise Latino, I love it - I feel like I'm back in Latin America, with all the different cultural, linguistic, and other aspects that come with being there.
I don't feel that English is really likely to lose its dominance in the US, but I definitely notice that speaking Spanish comes in handy more often now than it did 10 years ago. What I don't know is whether this trend will continue, and we'll move more and more towards a bi- (or more) lingual society, where speaking Spanish will become more and more useful as the pockets of Spanish grow and grow, or whether we'll follow the historical model of assimilation, with English staying on top.
