We just made the trip from Central Texas. The best prices for fuel was in the Baytown, Tx area. You can have your pick of truck stops. No surprise the road is in terrible shape. Houston to Orange and I-10 at Baton Rouge are a toss up as to which roads are the worst.
There is a Sam's just east of Baton Rouge, that has good fuel prices. It joins a Bass Pro Shop, therefore easy in and out. They are surrounded by places to eat or enough room to park and eat in the camper.
Just a note, we paid $4.20 for diesel in Florida.
Make trip during the day if possible, as I-10 in Ala., Miss and Fla. are a sight to behold. I thought Fla. was flat, but the northern part of the state is rolling hills and pine trees.