According to the thread below, he speaks only Spanish at home:
Which Potential Candidates Speak Spanish—and Will It Matter? (Bush speaks only Spanish at home)
http://www.freerepublic.com/focus/f-gop/3237220/posts
My wife is from Venezuela so we speak three languages at home: English, Spanish, and Spanglish. For example we call toilet paper "papel de tush." Oh, and there is almost no papel de tush to be found nowadays in Venezuela.