Patient Portal; js block. Locations Diagnostic Clinic Medical Group offers 5 convenient locations throughout Pinellas County. 5 Convenient Locations. Largo. 1301 2nd Ave. SW. Largo, FL 33770 (727) 584-7706. Call (727) 584-7706 Countryside. 3131N. McMullen Booth Road. Clearwater, FL 33761.