K.F.
I did Gymboree with my son (starting when he was about 6 months until a little past a year) and he loved it. I only stopped because we moved too far from the location in Plano to be convenient anymore. I thought the teachers were really good with the kids and the activities were very developmentally appropriate. I don't have any experience with the others personally, but I have a good friend who went to My Gym and really liked that as well.
Hope that helps!
K.