There are a number of ways to get from Paris-Orly Field Airport to the main IETF Hotels (Hotel Concorde La Fayette and Le Meridian Etoile).
Taxi - (cost is approximately €50 and the trip is approximately 40 minutes):
There are Taxi Ranks at Paris-Orly South, exit M, and at Paris-Orly West, exit B Arrival level. Fares increase by about 15 percent at night, and on Sundays and public vacations.
Air France Les Cars Bus (cost is approximately €10.35 one way, and the trip is approximately 45 minutes):
The Air France Les Cars bus to Hotel Concorde La Fayette and Le Meridian Etoile is “Line 1” (Paris-Orly to Etoile) and the stop is “Etoile.“ Find the bus stop at Orly Sud (Orly South) exit L; Orly Ouest (Orly West) arrivals level exit B-C. PLEASE NOTE: The Air France Les Cars Bus from Paris-Orly Field Airport does NOT let off at the Concorde La Fayette. The final stop is Etoile at the l'Arc de Triomphe. You then can either walk up Avenue de la Grande Armee (approximately 15-20 minutes) OR take the Metro (line M1) two stops to Port Maillot (direction La Défense / Grande Arche) (approximately €2).
Bus/Metro (cost is approximately €9, and the trip is approximately an hour):
At Paris-Orly Ouest get the RATP Bus (Line: ORLYBUS) direction Denfert Rochereau.
At Denfert Rochereau get on the METRO (M6) direction Charles de Gualle Etoile (L'Arc d'Triomphe).
At Charles de Gualle Etoile change METRO lines to M1 direction La Défense / Grande Arche, and get off at Porte Maillot (Palais de Congres)