We drove to WDW from Houston in 2009. It was about a 16 hour drive but we split it over two days stopping just outside of Tallahassee, FL for an overnight stay at a Holiday Inn.
If you plan your driving so you hit Houston between 10am to 3pm-ish you should be miss much of the traffic from the morning/afternoon rush hour. Don't bother trying to take I-610 around downtown as I found i-610 just as bad throughout the day many times when we lived there.
If it was me.... here's what I do.
- Drive to Katy, TX (just west of Houston) Thursday afternoon and spend a night there. San Angelo to Houston is 6 hours alone.
- Get up Friday early and hit the road by 4am to get through Houston. Early because you still want to get to Beaumont before rush hour. Takes about 45-60mins to get through Houston completely then an hour to Beaumont. You'll probably hit Beaumont at 6am or so and might catch the early bits of rush hour but hopefully can beat most of it. Once you're out of Beaumont it's pretty much clear sailing till Baton Rouge. You'll see some traffic there probably any time of day.
- Take I-12 to bypass New Orleans, then Mobile is usually quick to pass through. At that point it's pretty much open road to I-75 then down to Orlando.
- You'll hit Tallahassee at about the 10/11 hour mark, or about 2-3pm.
If you wanna keep going, you're about 4 hours from Orlando at this point.
Otherwise, I'd stop and stay a night here to give yourself a break, or in Quincy or Marianna just west of Tallahassee. We stopped at this
Holiday Inn Express in Quincy.