Hi Joyce!
Thanks for stopping by the Disney Parks Moms Panel.
Stroller Rentals at Walt Disney World are nice, because you can just drop it off before leaving the theme parks. Then you don't have to worry about folding up your own stroller on Disney transportation.
The Disney rental strollers do not have stroller locks. Sometimes Cast Members need to move strollers around in the stroller parking area. I do recommend bringing something to differentiate your stroller from the others like tying a bright ribbon or handkerchief around the handle.
Also, do not leave any valuables in your stroller while you are riding attractions. We usually bring a backpack to hold wallets, phones, and cameras and take it with us on rides.
If you have any other questions, please come back and see us real soon. Have a magical vacation!
Tania