Some may... But most won't, usually they have parakeets, conures and sometimes a larger parrot like an eclectus. I've never seen one at a petco/petsmart. Your best chance at finding one would probably be:
A. Local Aviary pet stores, not a huge chain like Petco
B. Searching on google for breeders in your area
C. Checking your local classifieds and Craig's List
I found mine through the classifieds where a breeder was advertising. I love my Lovebird!
Does anyone know if they sell love birds at petco?