If you get this vibration while braking, especially down hill, where the steering wheel shakes like it's turning right to left in fast short shaking like motion, the problem is more than likely wore out bushings on the "front suspension lower arm tension strut" (I believe this is what it is called) It is the bar which has the flat area where it bends slightly, a nut at each end, one end goes through the body or sub frame mounts, with large rubber bushings, large washers and lock nuts with the threads of the tension strut is visable. The other end goes through the spindle yoke, has a longer cap type nut which bottoms out and no threads can be seen on that end. You should replace the bushings on each end of this tension strut. This is a fairly common problem, at least it was with the two birds I've owned.
It's not that hard of a job but you will need to have the car aligned after replacing the bushings and re-installing the bar. Marking the location of the lock nuts before you remove the bar and (using new lock nuts) installing them in the same position will put it close, but you should still have the alignment checked by a qualified front end shop.
Good luck