A B757-200 Captain reported deviating from LAX approach course to minimize wake vortex from preceding B747.

Narrative

We were advised that we will be preceded by two 747s on our approach. LAX was conducting night visual approaches. We had been vectored and slowed extensively due to traffic saturation on all approaches to the 24s and 25s. Radio frequencies were quite busy. We were on downwind approaching 2;500 FT when the Controller called our traffic and asked if we saw the traffic or the airport. We responded by saying we had the airport and the traffic. We were given a right turn to heading 160 and cleared for the visual 24R. We had been experiencing some wake turbulence from the proceeding aircraft; and the traffic I believed to be the traffic we were to follow made the square turn to final prudent to maintain separation. I executed my square turn as late as possible due to proximity of the proceeding traffic; and flew through the localizer by approximately one dot (south) of the final while wing up base to final. At this point the Controller advised us we had gone through the localizer and to turn to heading 270 and re-intercept the final. We had already begun to intercept the final when the instructions were issued. As I flew down the final it became clear that the aircraft I was spacing off of was not the intended traffic we were to follow; but parallel traffic on 24L or 25R of which I do not recall being advised. Final approach was joined and conducted to a normal landing. No TCAS RAs or TAs were received. Controller was polite and professional and sent us over to Tower frequency.