You have to be pretty decent if you want to be in the beginner CAL league at the minimum. I used to be in CAL-O (stands for open; which is the for beginners in CAL) back in my old 1.6 clan. Even at O, teams were usually decent and you're going to require a bit of skill to compete fairly (although in my honest opinion 1.6 and source are pretty damn different).

I've seen you play Vince, and you're pretty good but I don't know how "good" CAL teams are in source (i only had experience with 1.6.