user: Question: What is average frequency MHZ when is in Portales, New Mexico?
Columns: ['Call sign', 'Frequency MHz', 'City of license', 'ERP W', 'FCC info']
Types: ['text', 'real', 'text', 'real', 'text']
Sample row: ['KFLQ', 91.5, 'Albuquerque, New Mexico', 20000.0, '[http://www.fcc.gov/fcc-bin/fmq?call= KFLQ FCC]']
SQL:

assistant: SELECT AVG("Frequency MHz") FROM "Table" WHERE "City of license" = 'Portales, New Mexico';