Not far from Keio Plaza is a moving walkway that helps get you to Shinjuku station during the day. Keio also runs a bus line called the "100 Yen" line that stops right next to the hotel and leaves from near where the airport bus arrives at the station (stop 20). But the Hilton and Century Hyatt busses are free and they are somewhat newer hotels.

Bear in mind that the walk is not a huge deal in any case and you pass through an interesting area of arcades and camera stores.

Nearby to all three hotels are the two Tokyo Metro Govt Bldgs, the tallest buildings in Japan, and the elevator to the viewing floor at the top is free! Also, there is a tourist office in the basement of one of the Govt buildings. There are many moderately priced restaurants at the top of the nearby NS building which has an interesting outside elevator. Other nearby tall buildings have restaurants on top as well, and one even has a club with what looks like an overpriced drag show. Avoid eating in hotel restaurants; the other nearby alternatives are cheaper and usually better but it's also a lot of fun, as noted, to buy exotic takeout at one of the department store food halls and bring it back to your room.