This is an old post and I'm a new user to this forum. And I'll try and answer this to the best of my expertise. I too have a WRT55AG Version 2 of the hardware. As far as all of your wired connection go, I think there ok. Securing your wireless transmissions and having easy usage for your guest will be difficult, especially if their are people you would like to keep out, like your competition. I only see two options.
1. Enable wireless security either using WEP or WPA TKIP Pre-Shared Key. Creating a passphrase (also known as a password), and giving this to your guest if they should want to