While mostly mountainous, southern Oregon has a well-maintained network of roads that connects most cities and towns. Biking is also an option, if you plan to be in the same area for a while. While in the Rogue Valley, for example, you can bike or walk along the Bear Creek Greenway, which connects the north and southern ends of the valley along the creek for which it is named.
More remote areas, including most mountain peaks and backwoods vistas, are accessible only by foot. Backpacking trails - including the Pacific Crest Trail, which runs north-south through the region's Cascade Mountains - are prevalent in most wilderness areas.