This hotel is located in the CBD of Beijing. If you want to take TAXI, may be a little more difficult.
However, if you want to go to Tiananmen Square and Forbidden City, try the subway. It may take you about 10-15minutes.
if you want to visit Great Wall, you can ask the hotel to arrange it for you. They can help you with the automobile and private guide.
The best way to major sites is and always is subway.
Finally, if I could comment on these Marriot Hotels in Beijing, I preferred Courtyard Beijing (in the center). for it owns the lower price and the best transportation.
The hotel is one of the best in BeiJing. I have stayed at the Marriott West end, the Renaissance, and the Courtyard and this is the best for location. That being said, it is the best for location to Tianamen and not to the Great Wall. You are easily, 20 minutes closer from the Marriott West end albeit farther from the airport.
I take cabs in BJ as they are cheap. Always carry the hotel's business card and most cab drivers can find it as the name is in characters. Writing using our alphabet is helpful for you to pronounce but utterly useless to a cab driver--or any Chinese speaking person. The ride to the Great Wall is about an hour and ask the hotel to arrange a tour at a palce other than Bad A Ling. That's where the tourists go and it is crowded.
JW Beijing is one of my favorites. It was actually my home away from home for a while since I've stayed there so many times in the past. Getting to and from the airport via taxi is fine, and there are always taxis in front of the hotel waiting so no problem there. Taxi fares are inexpensive, but traffic is horrendous in Beijing. As to getting to Tiananmen Square, Forbidden City, and Wang Fu Jing, best bet is to take the subway located at the nearby mall (Shin Kong). Great mall with food court downstairs as well as various high-end restaurants on the top floor. There are also restaurants right across the street from the back of the hotel, one of my favorites called South Beauty.
Hotel staff are wonderful, lounge is great, health club is better than norm, and just all around one of my favorite places to stay in Beijing...