In SA go to mission San Jose and Conception, they offer the best photo ops. At San Jose be sure to check out the arches by the chapel. There are great shots to be had there. The arches are in 2 stacked rows and offer great shadow and light effects. Take some real constrasty film and you will get great results. The alamo at night offers some interesting lighting and well (please do not demote me further) In Houston the park close to the zoo might offer you something but nothing special. If I had a large format camera I would head a little south of houston to either Pasadena or Texas City (Toxic City to people form there) and shoot the refireries from a distance at night. The sky line of the refireries is something unique and can be quite interesting!!!