By definition, you can only care about your own preferences. That being said, it's certainly possible for you to have a preference for other people's preferences to be satisfied, in which case you would be (indirectly) caring about the preferences of others.

The question of whether humans all value the same thing is a controversial one. Most Friendly AI theorists believe, however, that the answer is "yes", at least if you extrapolate their preferences far enough. For more details, take a look at Coherent Extrapolated Volition.