If you are to commute...go to Manila City Hall and you could take the G liner bus or RRCG bus lines...
If you are driving you may take from Intramuros go to Legarda then Ramon Magsaysay Blvd...then you make a right when you reach stop and shop and follow the jeepney route of Pasig-Quiapo going to the direction of Mandaluyong City via Shaw Blvd...then when you reach the intersection of EDSA and Shaw Blvd. you have 2 options...either take the overpass and make a left at San Miguel Ave to enter Ortigas Center or take the Edsa route by turning left and then at the service road make a right at Julia Vargas Ave to enter Ortigas Center...good luck.