Update. We just did the rest of this trip to the Bolivar Peninsula via I-10, Texas 124 and Texas 87. This would be the most likely route to Galveston on the ferry.
I-10 was good and bad. The 5 miles either side of Breaux Bridge LA (exit 109) was thump-thump concrete. There were rough sections through Lake Charles and Beaumont TX. The first 2 miles in Texas were construction squeezed lanes. Other than those spots and the afore-mentioned bad patch of I-12 in Baton Rogue, it was pretty smooth.
Texas 124 and 87 are fine 2 lane road flat and well paved. Motor safely.
