requirements- "Lived in Texas three years prior to high school graduation or obtaining a GED from Texas or
Resided in Texas the (full) year prior to enrollment in an institution of higher education
Provide an affidavit stating intent to apply for Permanent Residency when eligible to do so"

If it doesn't work out for you, can't you just go take your GED. And prove that you've lived in Texas for 3 years prior to that, and get in-state tuition that way?