I know you said you would prefer to go straight to PhD, but if you were to consider starting with an MA and wanted to do socio, I would say go to NCSU (http://www.ncsu.edu/linguistics/). I graduated from this program (so yeah, I'm biased), and it is wonderful, to say the least! It's a really small program (there were 15 MA students there when I was), it's a relaxed environment where you can pursue your own interests (or join any of the existing research projects), daily interaction with profs, and lots of student collaboration. PM me if you want to know more!