I recently discovered how to commute from SM Megamall to Greenhills Shopping Center via the Van Terminal located at the back of SM Megamall A. It is located at the public parking lot of St. Francis Square just across the back exit of SM Mega A. Think of National Bookstore, flower shop etc.
Fare is only Php20.00. I find it much more convenient than walking or riding a bus then crossing Edsa.
Have a safe trip! God bless us always!