I visit Islamabad annually and used to stay in hotels til a few years ago! Was recommended to save money and stay at a Guest House. Was given tel no for Shelton House, Kaghan Road nr Faisal Mosque. Called them and booked a room for family. Met at airport by car. Got to guest house , lovely large house. Cost Rs/= 1000 per rm per night (GBP 10.00!)LARGE room, en suite Clean bathroom. Lovely balcony. Felt we were LIVING in Islamabad. Very hospitable staff and felt we were their personal guests. Could walk to Faisal Mosque and local shopping area.
Caught official cab from local road junction daily and went for 'ziyarat' (tours of city). Found places to eat on these tours (could have any meal at guest house at xtra cost/in room only) if we wanted. Tried once, nice but not cheap (slightly above average). Would recommend trying out guest houses (nice alternative if you don't want the frills of the hotel foyer etc.) more