The downtown area is compact, and the museums and most restaurants are within easy walking distance of the main hotels and many of the B&Bs. Public transportation by Atomic City Transit (http://www.losalamosnm.us...){28616E25-1EBA-4043-8BA9-8FAD23800B74} is free and includes both fixed routes and an on-demand service.
Many Los Alamos residents bicycle to work and around town. Cycling is feasible for visitors as well, but be aware that the town is at an elevation of about 7320 feet 2231 meters and quite hilly. Puffing up the hills before you've acclimated to the altitude can be a surprisingly exhausting experience.
Road cycling is popular here, and some competitive road bicycle racers come here to train. Popular routes include NM 502 between Los Alamos and Pojoaque, and Camp May Road up to Pajarito Mountain Ski Area. White Rock is nearly a thousand feet lower and about 10 miles 16 km away by road; riding to it on a bike can be a thrill, but oh, that hill coming back! From White Rock you can take a bus back to townsite: Atomic City Transit buses are equipped with bike racks.
Los Alamos County has an extensive trails network that is open to mountain bikes. The network is especially well developed around townsite, and connects to trails in Santa Fe National Forest and Pajarito Mountain Ski Area. In summer and fall the ski area offers lift-served mountain biking: ride the lift up and bike down easy sideslope trails or bomb down very challenging trails designed specifically for mountain biking. The ski area also has a mountain biking terrain park.