Check out Provident Living Home
There you can search for a cannery near you and find out their hours, and if you need an appointment. I know at the one near me (Portland, OR) you need to have an appointment made, and you have to come in a group of eight, except for Tuesdays (or Thursdays? I forget) when they allow "walk-ins".
On the website also you'll find an order form which gives you prices according to how much you want, and what kind of packaging you want (cans or mylar bags). The cannery staff LOVE IT if you fill out one of these order forms beforehand and bring it with you when you do your canning so they know how many bags of food to bring out for you to can.