I've stayed at the Sofitel Porte de Serves in Nov 2003- my friend's and my first trip to Paris. We were on RyanAir (from Dublin to BVA - don't ask) and once we were dropped off in Paris at Porte Maillot, we took the Metro (Line 1 with one transfer at Concorde to the Balard - Line 8) to Balard station and walked the 7 - 10 min walk to the hotel (it was around 9pm at nite) and didn't feel in any way threatened. In fact, along the route is some kind of military or government complex w/ uniformed guards 24/7. The only part I felt a bit nervous was at the crosswalk at the on-ramp to the Peripheque.
Never arrived back at the hotel before 9pm during our 3 nite stay and we always took the Balard line back (we are both middle-aged females who are between 5 ft and 5 ft 3).

Enjoy Paris.

RxTravel