They're mostly heading up to the West Texas area between Lubbock and Fort Worth. I've gone through the area each summer and it seems like there has been an explosion in the total number of windmills over the past two or three years. Not only does Texas produce twice as much wind energy as any other state, it has been growing at an increasing rate of 1GW-1.25GW every year for the past four years.
For an insightful (and sometime humorous) look at the direction Texas is headed with wind power, check out this interview
with Texas Land Commissioner Jerry Patterson.
"I talked the Audubon Society and told them, "Don't worry about this, after several generations we'll have smarter birds." They did not think that was funny. The other thing I told them was wind farms in the Gulf of Mexico would be the first line of defense against avian flu. These people have no sense of humor. You can't break the ice with them."