Moving access to crawl space
It appears to me that all of the vertical walls are load-bearing. If I assume the roof to the crawl space is a reinforced concrete slab, it's live and dead loads would likely bear parallel and perpendicular to the side walls. 

You can move the opening. But because the existing construction of the crawl space roof is unknown and, like-wise, exactly how it bears on the walls, I suggest you create the new opening in a mirror image to the existing opening. In other words, from your picture, use the measurement from the left side of the opening to the wall to the left as your new right side opening measurement from the corner, but do add to that length the width of the the wall. 

Lastly, yes it would be more difficult to do the work after adding the new AC compressor because it is best to fill the existing opening with load-bearing material, such as concrete block, and finish the exterior to best match the walls. Once that's finished you won't have a possible interference with the AC compressor.