I've noted that Austin zip code 78741, unlike 78704, saw its population of children surge between 2000 and 2010. Given this chart, it should be no surprise that its Hispanic population also surged, from 20,966 to 27,913.
Here's the breakdown by Census tract:
Hispanics also rose as a percentage of 78741's total population. In 2000, Hispanics made up 52% of 78741's population. In 2010, they made up 62% of 78741's population. The breakdown by Census tract shows a lot of variation, though:
Hispanics made dramatic gains in Census tracts 23.13, 23.14, 23.15 and 23.16. They clearly have been displacing some other demographic in these tracts. Or perhaps "replacing" is more apt. Each of these four Census tracts had a high percentage of college-age kids in 2000. In fact, they had four of the five highest percentages in 78741. I suspect that Hispanics moved into these tracts as college students left for new housing closer to campus. I don't have the data to confirm this yet because the Census Bureau has not released full data files.
I think we can draw one firm conclusion from this data. Although 78704 lost children and 78741 gained chldren, this was not caused by migration from 78704 to 78741; 78704 did not have enough Hispanics in 2000 to account for 78741's growth. The migration of families with children into 78741 was merely parallel to the migration out of 78704.
(*Note: Census tract 23.11 was split into tracts 23.17 and 23.18 for the 2010 Census. I combined them to allow comparison between 2000 and 2010 data.)