I've seen buzz many times in MK around the corner from "his" ride. Walk down the "road" like you are heading back to the hub and he is on the left right before the bridge.
I've also seen him on the next "spoke" up - in the same spot (which is outside the restaurant)..can't remember the name - used to be tomorrowland terrace (I'm showing my age.
We saw Buzz and Woody at Al's Toy Barn. But as the pp said, it can be quite a wait! We got in line just as they went off for a break, so we had to wait for probably 30 minutes or so... Good thing for us it wasn't a hot day because the line was completely in the sun. It was well worth the wait though, my (then) 3.5 yr old was BEYOND excited!!!!!!!!!!!!
At MK Buzz stamps his autograph in the area between the teacups and Cosmic Rays(?) restaurant. It isn't really even an area you would expect them to have a character signing but ask a CM. When Buzz comes out you want to be in the right area because the line can get long.
In April we saw Buzz right across from the teacups. Got his "autograph" in books and a Buzz tank top(son's)! We also saw him at Al's Toy Barn in MGM - you can ALWAYS find him there! Got him to "autograph" a Buzz shirt for my nephew there. How cool is that for all Buzz fans??