This is partly a difference between AE & BE. "Attitude toward" is almost always safe in the US.

I hear "attitude to" from UK speakers, but not often from US speakers. I never use "attitude to" myself.

Attention: In the U.S., attitude is something negative! Just wanted to mention that, because that's a big source of misunderstandings ;-) This seems to be completely unknown in German-speaking countries, not even my Langenscheidts Großes Schulwörterbuch mentions this.

I don't know whether that is the case for Britain as well, though.

Maybe this sounds obvious to native speakers, but for Germans it obviously isn't.
Here's an anecdote to support my point:

I once saw an interview with Heidi Klum in an american news show, where she said that for women being successful in business was just a matter of attitude. After the interview, the anchorwoman found it necessary to inform the audience that this was attitude as in "a positive attitude".

I found that very amusing :-)

@abc: I suppose that goes to show that people are so inundated with rap slang that they no longer understand their own language.