We drove down last year. We're about 40 miles east of San Antonio on I-10. We left about 3am to make it through Houston before the traffic. We stopped after about 15 hours in Marianna FL at the Hampton Inn. The hotel was really nice and Hampton Inns have a pretty nice continental breakfast. If you stop here do NOT eat at Ruby Tuesdays restaurant...it is awful.
Speed limit is 70 to 75 once you leave Texas, and we stopped about every 1 1/2 hours for a few minutes for restrooms and beverages and stopped for fast food lunch. We left Marianna about 8am and got to WDW about 1 or 1:30 that afternoon.
On the way home we stopped in Baton Rouge, also at a Hampton Inn. It was near a very good Cracker Barrel restaurant.