It does not seem like a good idea to me. When no one is home the porch may give some cover to a thief who wants to take your bikes. So he has ample time to bypass the locks. Locking bikes with a cable on a porch is similar to giving them away In most places. The cable is only protection if someone is watching. Most things that you can attach to a wooden wall are not too hard to get off of the wall. Maybe a huge eyebolt that goes all the way through a stud and is nutted on the inside of the wall? Then use Kryptonite NY locks? Or a New York chain? Even then I would prefer to bring them inside if possible. Taking the front wheel off will make the bike smaller and lighter, maybe that would help going up the stairs. Try a frame pack or bag. It fits under the top tube and allows you to balance the bike on your shoulder with a padded strap.

Keep a rabid Doberman on the porch?