Buzz hangs around near the exit of Buzz Space Ranger Spin ride. We've seen him when the parks first open. I'm sure he's there other times too.
You can meet Woody at the old Diamond Horseshoe saloon that housed Goofy's Dancing Jamboree. It's now a meet and greet place for Woody, Jessie and Bullseye.
Woody, Jessie and Buzz are also at MGM at Al's Toy Barn, on the right side of the Muppets 3-D exit area. They're also in the Stars and Motorcars Parade at MGM.
If you're lucky enough, you can also see the Green Army Men. They will sometimes patrol the area with their green truck. Once they were actually in the MGM parking lot directing traffic!
Have fun!
PS: you should be able to find Zurg at MGM at the last store on the right before you turn right towards Tot, MK at Buzz ride giftshop, and at World of Disney at DTD.