Tried skimming some of your thread, you mentioned you want snorkeling locations in the upper keys. First off, there are no beaches worth going to for snorkeling in the upper keys. Everything is off shore. And really , you can get out there with your zodiac , at least I wouldn't recommend it.
So with that, if you know how to navigate a boat well then rent a boat or book a local charter.
The best spot in key largo is Molasses reef, varied depths and a lot of life! If you go on the weekend on a good day there might be a lot of boats though. Still the best spot hands down though. I always take my friends there and everyone loves it.
We have a lot of different places here, to cut down the list and make it easier I'm going to post a link.
http://www.rainbowreef.us/dive-locations-in-key-largo/
This is a good starting point.
A spot that isn't mentioned there that is in reaching distance for your zodiac is a shallow exposed wreck right off Garden Cove , which is in the upper part of key largo before Elbow reef and dry rocks.
Regarding the months, I prefer August over Oct/Nov any day. From Sept to Jan the chance for jellyfish increases like crazy.. You are guaranteed to see during those months. Which is why the snorkeling charters give a lot of deals during those months. I've been out during Sept and Oct and you literally swim in a sea of jellyfish. I gave up on going to the reefs/ocean side during that time period. I don't mean to scare anyone but I'm talking hundreds/thousands of them. Maybe you get lucky and there's none or very little that day, that's awesome. But I wouldn't want to go out and spend the money/fuel to take that risk, it turns a great experience into a bad one.
Enough about the jellies, Oct/Nov/Dec is also great fishing for Sailfish. What does that mean? A lot of wind! Most of the reefs are on the edge which mean that can also turn it into a bad experience. Also, the water will be very turbid.