They do have an aquarium section by the bathrooms in the back of the store, left of the electronics. They do have a great assortment but whether or not they are female, you may know that.
I haven't seen live fishes at Milpitas Walmart in a long time. You might be able to find some guppies at PetSmart located in the same plaza as Walmart.
Thanks! Your answer is awaiting moderation.