NO! You will do all sorts of nasty stuff to the car, from scrubing out tyres, to destroying the transfur box. Part time 4x4's like the Sporti, Vitara or series Land Rover are not designed to be used in 4x4 on solid surfaces. Permanent 4x4's like the Discuvery use a 3rd diff in the transfur box to alow all 4 wheels to turn a diffrent speeds when cornering. Without this you get 'transmition wind up', putting a lot of strain on the drive chain when driving on roads.
What you can do is take the othe FWH apart, and permanently lock that too. Then drive in normal 2wd. This will pull you performance down as well as you fuel consumption (though not much) as the front drive chain will still be turning, but it won't break the car.
I am not sure what would happen if you drove with one FWH locked, and the other free? I'm guessing it would prob bust the unlocked hub, or the drive shaft. I'm only guessing here, but I think the locked hub would turn it's drive shaft as you pull away. The diff would then turn the other driveshaft in the opposite direction (as this would be eisier that turning the prop). The other hub would then try to engagwe as if you were reversing in 4x4. As soon as it engaged ther would be no drive (as the diff would then put spine from locked hub to the prop (path of least resistence). The working hub would then unlock. Repeat lock unlock thing until something james at speed. opps busted hub / drive shaft / diff?

What you could do is replace with manual FWH. Beware though second hand ones may not fit. All manual hubs I have seen are 5 stud to the hub proper. I am lead to belive that most auto hubs are 6 stud. Mitsubishi are 6 stud, as are Suzuki. But I don't know if either will fit. Prob not, and I have never needed to look into it.

Any veiws expresed in this thread by me are purely from my own experience, and (sometimes) falible memory. Hope my comments help, but please don't take them as gospel.