As the others have already stated, the location pictured is on NW 25th street just past the US customs building on the left. NW 25th st. can best be reached by taking Milam Diary Rd which has an exit from the 836 expressway on the south side of the field or from NW 36th st which runs along the North side.
>>>>>CAUTION <<<< to anyone planning to go there in the immediate future: I too have heard that the police are detaining and questioning anyone they see near the perimiter fence, EVEN in the designated area pictured. I spoke to a fellow spotter yesterday who was held, questioned then told to leave the airport area. There are no warning signs indicating anything is different, just the sudden appearance of Miami/Dade police with lights going, followed by detailed questioning, taking down of your name, address, etc. then a polite invitation to leave the area and not to return for a few weeks. :-(
Good Luck !
Graham Hitchen, KMIA