Killeen is a car-dependent city and you will need a vehicle to do anything useful here. The city has no meaningful public transit, and distances between points of interest — particularly between town, the lakes, and the base — are too large for walking. A rental car is essential if you do not have access to a private vehicle.
Driving in Killeen itself is straightforward; traffic is light except near the main Fort Cavazos gates at shift change times (typically early morning and late afternoon on weekdays). For the lakes, US-190 east from Killeen leads towards Belton Lake, while Stillhouse Hollow is best reached via FM 2410 heading south. Belton town, about 15 minutes southeast, has additional services and restaurants.