You could put free rolling wheels under the skirt so that on start-up, the skirt lifts the robot off the wheels. Also you could use several of those silver motors to power a centrifugal fan similar to this one. They are commonly used in commercial hovercraft and are more efficient at this task than a vacuum or a typical fan partially because it disperses the air evenly. Then use 2 cim's per fan for propulsion in a dual rear fan set-up.
Here's the type of fan I'm talking about.