Does the Dragon reusability concept of SpaceX include the ability to reactivate the engines after landing to make a "jump" to a new soft landing location some kilometers or so away on the surface?
Is it (will it be) capable of hoovering at low altitude over the landscape for tens of minutes to for example get feedback from human control on Earth to Mars?
Or is the Dragon concept designed just to make one soft landing, not able to take off and land again without refurbishing?
Yes, the SuperDraco thrusters are restartable. The propellants used are MMH (Monomethyl Hydrazine) as fuel and Dinitrogen Tetroxide as oxidizer which are hypergolic, meaning they ignite on contact with each other and that greatly simplifies engine's ability to restart, throttle and achieve full thrust in quoted 100 ms.
Ability to hop from one landing site to another and hover will of course depend on amount of propellants available for such maneuvers relative to vehicle's payload mass, gravity and atmospheric density, i.e. achievable engine efficiency given specific conditions and thrust to weight ratio for a specific mission.
Since they'll be used on DragonRider, the crewed version of the Dragon spacecraft, their target performance will have to match requirements for LES/LAS (Launch Escape System / Launch Abort System) for human-rated vehicles, and SpaceX has plans to soft-land them on Earth as a part of their fully re-usable launch vehicle (Falcon 9 and later Falcon Heavy) once returning from LEO orbital speed to a soft landing in Earth's gravity, so I would imagine hovering and hopping could also be achievable on the Moon or Mars in reduced gravity w.r.t. Earth's surface.
One note though, that there would be little point in waiting for Earth based control station's communications to Mars during critical maneuvers like this. Depending on Mars' position relative to the Earth (closest at ~ 54.6 million kilometers), one-way communications delay is at minimum roughly 3 minutes. Mars landing craft will require far greater autonomy than having to hover over some surface to wait for input from Earth.