There is little evidence of public transport here, but taxi or car service is available. The city is a 15 km long line along the highway, so very little is walkable. The countryside around the city (e.g. the highway to Abha) has a large number of police checkpoints to combat smuggling to/from Yemen; police escorts for tourists are common, and not as much fun as they sound.
Although the city is the closest major Saudi city to the Yemen border, land travel across may not be possible, and is certainly not recommended due to the high level of violence in the area.