M20 pilot departing MYF reports a NMAC with a Cirrus entering the pattern. Evasive action is taken and the event reported to the Tower.

Narrative

I was cleared for takeoff on Runway 28R for an eastbound VFR departure. (This departure calls for a westbound takeoff followed by a climbing right turn to the downwind; remaining south of California Route 52; and exiting the pattern eastbound.) On takeoff; I began my climb; maintaining visual separation from a slower airplane in the upwind from Runway 28L. Upon reaching California Route 163; I began a climbing right turn. At approximately the crosswind point of the turn; a Cirrus crossed my flight path from my left to right (east to west); approximately 300 FT horizontally and between 50 and 100 FT vertically from me; requiring me to take evasive action to avoid what appeared to be a collision course with that airplane. No traffic advisories were reported from the Tower prior to; or during; the takeoff; and it's possible the Tower was not aware the aircraft was there. (During my run-up; my wife; also a pilot; recalled hearing the Tower clear a Cirrus over Mt. Soledad for landing on Runway 28L. If that's correct and the subject plane was that Cirrus; then he would have entered the pattern from the incorrect side of the field; and north of the Tower. The controllers would have been looking for him to pass south of the Tower from the Controllers' right to left.) Once clear of the Cirrus; I returned to my climbing turn and continued downwind in the pattern; maintaining visual separation from that airplane. As I cleared the pattern eastbound; I observed him descend; and it appeared he began to cross over the runway environment at which point I lost sight of him. I reported the event to the Tower and continued my flight with no further issues.