Is there a class E corridor in the class B north of San Diego International?
I'm a frequent VFR owner/flyer in that area for past 12 years. The box is clearly identifying the floor within in the box it is pointing into.  That 1800/3200' is to keep transitioning aircraft either below or above the MIRAMAR MCAS departure corridor.  Aircraft that are inbound to Montgomery Field will often transition with a Class B clearance when flight followed by SoCal on 119.6, at 2500-3000'  Inbound commercial jets for Lindbergh Field will come thru that zone at 6800' and above. And yes, as depicted on the chart, offshore of Torrey Pines and west of the OCN 152 radial, the floor is 1800'.  If you're looking for a "corridor"to the South Bay onto Brown Field, you could fly the shoreline at 3600'-4600', from Del Mar, over Mt Soledad, and then join the VFR corridor over Lindbergh Field, and onto Brown Field.