The warnings against AI are overstated. It's fine to start off playing AI. By the time you're out of the 20K range, you'll start noticing that you're only winning against AIs your level because they're acting dumb. It isn't good to scare off beginners. Especially as it can feel a bit tense, playing online. AI warning is good for better players, but they should know better anyways. The real issue with AI is finding one worth playing as a beginner, especially on 9x9. Sure, you can take a big handicap, but I'm not sure there are any useful AIs at that level to have even games with.
Another good resource is DGS : dragongoserver.net. An open source turn based (correspondence) Go server. It's easy to play as there's no time pressure, and you can fire up several games at a time.