For artists/writers plus internet connection you'd have to try Mexico City.... if you don't mind going insane. The sad truth is, Mexico isn't very big on art producing.
But where would you like to go? Tropical jungle, beach, urban zone, desert, etc, etc? I know of a beautiful place in San Luis Potosí called Xilitla, my ultimate writing dream is going there for a month and writing. It is located in the middle of a jungle, in a mountain, and it is such a magical place. There are also a number of cool, awe-inspiring, creativity-boosting atractinos nearby, such as the giant surrealist concrete statues and a cave full of birds (golondrinas? anyone?) And I know for a fact there is at least some internet in the town, although I'm not sure about speed. Most of Mexico still uses dial-up for everyday internet.
Here, pretty picture of the concrete statues in Xilitla:
And, well, they get a lot of foreigners, so I think you should be fine. If you don't speak any Spanish I suggest you stick to the big cities and/or frequent tourist spots. But really, what kind of climate do you want?
If it's a beach you want maybe you'd want to consider Mazatlan, Zihuatanejo (that's where Melaniehoo is), Cancun, Acapulco, Puerto Vallarta or Los Cabos. If you like tropical but not really beach then I can recommend Ixtapan de la Sal or Valle de Bravo. They're big tourist places so you'd get English-speaking people, and they're all beautiful places.
