Hi ...I too went out of state for my surgery it was a 3 hour drive for us...and I was in the hospital for 5 days and was able to cope with the ride sitting in the front passengar seat with the seat reclined but using a big fluffy pillow that had me more upright then flat....and I was ok......the pillow helped keep my head from bobbling all around on the bumpy roads.
I am sure when your Dr releases you to drive home, the laying flat rule is ok to omit until home. The rule pertains to being up and walking not so much the reclined position so you should be fine.