I'm surprised to find no one has created a thread regarding Houston yet :D.
Probably THE best place to sample nearly all the fragrances possible is the Galleria Mall. Some stores located inside include:
Neiman Marcus- some of the friendliest SAs I have ever met!
Yves Saint Laurent
And many, many others. I spent nearly a day there and still haven't explored the entire shopping center.
It's located at 5085 Westheimer Rd, Houston, TX 77056.
I highly recommend swinging by there and setting a day aside if you swing by Houston!!
PS- their Oakley store is also quite nice *wink*