the easiest would be via commonwealth. You just cruise through the whole avenue and you would get there. traffic during rush hours.
BUT
the fastest would be via C3, theres this secondary road, but I doubt if you would be able to negotiate that. Sorry can't describe it further, its a shorcut..
From Monumento ride a bus, get off at GMA kamuning - before the bus gets on the flyover.
Walk a bit going to East Avenue - its on the left side under the bridge. Board a bus going to fairview...
OR
Get off at SM north edsa and go to the FX terminal ( within SM compound). For sure theres an FX bound to SM fairview there.
Happy trip!