No one knows where Emlin's Alley was. It was probably the same place listed in the 1791 directory as Emlen's Court, which was in the Northern Liberties. In any case, both are listed here.
(1785) #1 Emlin's Alley, Savoy, Widow
(1785) #1 Emlin's Alley, Shaw, Widow
(1785) #2 Emlin's Alley, Baxter, John
(1785) #2 Emlin's Alley, Palmer, George
(1785) #4 Emlin's Alley, Pertheus, Plas
(1785) #5 Emlin's Alley, Barbin, Widow
(1785) #6 Emlin's Alley, Robinson, Widow
(1785) #7 Emlin's Alley, Requier, Frank
(1785) #10 Emlin's Alley, Carpet, Armond
(1785) #14 Emlin's Alley, Cerneau, Widow
(1785) #21 North Emlin's Alley, Harman, John
Emlen's Court listings (1791):
(1791) #1 Emlen's Court, Stone, William, ship carpenter
(1791) #3 Emlen's Court, Pamus, John, hatter
(1791) #7 Emlen's Court, Town, Benjamin, shallopman