He is either on Wimpy Wonderland or Wimpy Boardwalk. Hope that helped.
In his house
in greg's locker
Bribe him with candy
Go up to Greg and click on are you going back out there then go to your backpack or whatever and give Greg the guide).
poptropica
start by clicking on Greg and Greg asks you to help him find his little brother,Manny
click on the curtains to open them.
you go to lushery towers.
Greg's locker combination is 9-37-15 if that is what you're looking for. You're welcome.
find out your self because i do not know
open the curtains
You have to go find Greg