How important is for web servers to be near your users?

Hi, I am going to hire a hosting service on behalf of the my school’s magazine. We where using a local hosting service (we are in México) which has worked well but I am implementing several changes which I believe will start to strain the shared servers. Plus, we are getting more users every week. Right now I’m thinking in switching to Media Temple as I’ve used them and they offer a great service and have a much more developed infraestructure.

About 90% of our readers are mexican, and MT servers are probably in the US or somewhere more far. So my question is, how relevant latency becomes with web servers. Will we feel the difference or will it be just not noticeable .01 second difference?

Thanks :)