Hi Jerry. I went to Galapagos last August. We flew Tame airlines from Quito to Baltra. You are allowed one checked bag that is weight restricted to 70lbs and you can take a carry on bag. I packed as much heavy stuff in my carry on as I could - my computers, regulators, camera, etc. I was a little over the weight limit, but the airline was pretty good about letting it slide or at worst paying 1/2 the fee.
One other option is now there is another airline that flies to Baltra. I can't remember the name, but the operator that is taking you into the islands should be able to tell you. A few members of our party flew that airline and they said they were not charged for overages at all.
Good luck and enjoy the diving, its awesome!
Kim