Houston was just about split in the last election (Obama won Harris County by 585 votes). Austin went heavy for Obama (60.2% to 36.2% or just under 100k votes). Houston has quite a ways to go before being liberal. The hispanic vote makes Texas as a whole pretty interesting though.
I don't care if Houston is 'Liberal'. I prefer pragmatic and reasonable. If the two go hand and hand, so be it, but I don't think that's always the case.