When Luke and C3PO find R2D2 in the canyon area, R2D2 informs them of several life forms headed their way. Luke concludes they must be sandpeople, so he...
Leaves the landspeeder and heads for a nearby cliff a few hundred feet away?
If the three of them had just gotten into the landspeeder when R2D2 told them about the approaching sandpeople, they could've been out of there before the sandpeople had a time to walk up to the speeder, slowly investigate it, and follow Luke up to the cliff for their ambush.
Why did Luke feel the need to lead the two droids away from their only mode of transportation, and an easy means of escape?