We were there last year the last weekend of Sept through the first week of Oct. No crowds...most everything a walk on. Of course, parks closed early, but really - we were able to see everything we wanted to. We also pulled the kids out of school (1st and 3rd grade) but won't do that again. It was such a pain to keep up with their packets of homework and they had absolutely no interest in completing them (who would??). Fortunately, they are awesome students and suffered no setbacks academically, but we just won't attempt that again. Also, with the series of testing done now in Texas, it is really frowned upon now because the entire school year is now devoted to preparing for the TAKS tests. UGGHHH.
OK..back on topic. Weather in late Sept couldn't have been more perfect. Warm enought for the pools, but not too hot to be so uncomfortable. Next June for us will be an entirely different story, I'm sure.