I don't mind at all if the safety demo is done both in English and Spanish.
I find it quite amusing that some people are irritated and offended by hearing the safety demo in Spanish.....don't you have anything better to complain about?
Just like when I hear announcements in Japanese at SEA on the air train....it doesn't bother me a bit that both signs and announcements are made in both English and Japanese.
If you really can't stand listening to it in Spanish...then put some ear plugs on and tune it out....it's a free country you know?
I actually zone out the english demos most of the time....I just make sure I know where my closest exit is and I'm already an expert in fastening my seat belt! :-)