Perhaps this is what is meant by Walmart. Many places like Walgreens, Wolf, Ritz, MotoPhoto Probably Target etc., offer services where you can email in your digital pictures and direct them to your local store. They will then print them for you and have them ready when you can come later to pick them up. I don't know how long it takes. My brother did it with some Hockey Photos through MotoPhoto last summer and it was done in a few hours to next day. I guess it depends on when you get them in and if the printing equipment has already been shut down or if there is a line up of work in the system.

Just make sure your images are plenty large for the size of images that you want. You will want 3mpxl or better for a 5x or an 8x. Have a 5 or 6 mpxl or better for an 8x or 11x etc. The larger the better, I would think. I am not sure if you have to actually resize the picture file to what you want, before you send it. Check with your local photo finisher and see what their specs are. Most places should have detailed instructions on their websites.