I'm pretty sure there will be a lot of Alliance EU players. Don't make your decision based on what you see on the forums, these guilds are "premature", lots of them will split until 60, new ones will be formed.
The lack of Alliance guilds on EU side just proves that EU Alliance players don't care at all about making a guild before launch. I didn't bother with Horde guilds either, I will choose later on.
9 years, you are sort of like the opposite of me.
11 years proud Horde player (okay, 10.5).
If I was the only player on Horde I'd probably still play Horde. Seeing your longtime alliegance you seem like the same kind of person to me.