Yes, you can see white pelicans in the wild in Houston

Here is the proof: The pelicans are back at the "water hole" between Highway 6 and Eldridge at West Park. Built for flood control purposes, and recently enlarged, this man-made lake has become popular with local residents for walking and biking shore-side, but also with birds. Their favorite spots are the little islands where no humans bother them. As was true in the Spring, though, great white egrets and ibises are more common than pelicans. You will need a powerful zoom lens to get close-up shots. 

Detention pond island birds: White egret, American white pelicans, more egrets 

Detention pond islands in the late afternoon (Sep 2015)

Great white egret strutting in shallow water 

Sunset at the detention pond