We just got back. It wasn't too bad midweek, tho on Thursday thru Saturday night you really needed to pick up a mooring by 1 or 2 PM, and lots of owners were coming across and punting off the squatters. Avalon was mostly full, and even Desconso was busy. I do NOT want a back row East mooring in Desconso; the boats there were thrashing wildly in even a modest westerly swell. Depending on your boat size (up to 26ft), you might ask about the shoreboat spots in Avalon, behind Casino mole. The Harbor Patrol sometimes forgets about these; we were able to pick one up about 4 PM on a Wednesday, and there was one more spot free. It can be a little rocky in daytime because of boat wakes, but it's real quiet at night.
At Isthmus, 4th of July is filling first, then Cherry Cove. According to Latitude 38 today
, the main Two Harbors field was absolutely sold out this past weekend for the first time, so things look grim for you. Again, the stringline is an option if you are under 26 feet. That's where we were, and it was only about 1/4 full. Harbors to the west are going to catch a lot of overflow, so they may be short of moorings.
Cat Harbor, OTOH, was nearly empty when we visited, and there was only one boat anchored in the northern shallows. This site
has webcams of Avalon and Two Harbors; if you mouse over "Current Conditions" and click "View Detailed Conditions", it will show available moorings for the everything but Avalon, tho it's not always up to date.
Heh -- we were the smallest sailboat at Catalina, which does have advantages. I'd advise laying in ridiculous footage of anchor rode, just in case you get skunked. Luck!