I guess it ultimately depends on the strength and stability of your wireless connection. Is it consistently strong and reliable? You might not be able to host games because it may be necessary to set up port forwarding on your router (for ports 6000, 6112, and 7000). However, that's not a very big deal since most people can host games.
The other issue is the strength of your computer. Do you have a good dual core processor and a lot of RAM? I play on an old Socket 939 Athlon 4400 (a dual core overclocked to 2.4 Ghz) and a pathetic 2 GB of system RAM and normally don't have any problems though my computer can tend to lag later in the game when numerous large fleets are out. (I have all of the settings turned down.)
Anyway, if you don't know anyone on ICO, it's not a problem. (You wouldn't be playing on LAN anyway if you don't know anyone who has the game.) Just register an account with ICO, create a user name ("Add User" I think), and come join the fun. Do note that Sins has low player counts. However, 4v4 and 5v5 games are played every night for the Diplomacy expansion. However, you have a greater chance of hooking up with new players on the original Sins but those games are mostly all 1v1s and 2v2s. (Mostly its friends who play comp stomps which you might enjoy.) There aren't too many people playing Entrenchment since most people who had Entrenchment purchased Diplomacy.
While everyone is welcome, you should probably make an effort to try to play against other newer players because the pros will thump you. (This game, especially humans v. humans, has a learning curve that you haven't been exposed to against the AI.) On the other hand, playing against the good players is really the only way to learn the game. Just try to follow more experienced players' advice, be gracious, and consider watching game replays. If you have already mastered Sins against the AI it won't be too hard nor take too long to learn the humans v. humans game.
