Can you get a mooring in Catalina on Memorial Day weekend?

I've never been to Catalina on Memorial day weekend and I don't want to drive out there and end up having to come back because they are all gone. I want to go this Mem day weekend for one night, maybe Saturday or Sunday night. I have a 25' Cabin cruiser. How hard is it to get one? I prefer Avalon. How early should I go?