Although the city sprawls, it does contain a handful of neighborhoods well suited to exploring on foot. In both Downtown and Old Town, you'll find plenty of garages and parking lots, and good areas to get out of the car and explore on foot. The same is true of the adjoining Nob Hill and UNM neighborhoods. For a short visit to the city, you could focus your time on these two areas.
The rest of the city stretches pretty far. Allow an average of 20 minutes to get from one part of town to the other. A helpful strategy is to bunch together more outlying attractions that interest you, perhaps hitting Bosque Brewing Co. and the Balloon Museum the same day you go out to Petroglyph National Monument or ride the Sandia Peak Tram.