Ganges is, of course, always a bit tough but we usually use the transient floats just beyond the Coast Guard station, right below the Thrifty's grocery store. They have added some footage and a second float a few years back and since many use these floats as a 'stop and shop' slips do open up from time to time. The most exposed float can be uncomfortable but there's no place more convenient than these.
It's also sometimes worth a look into the original fishermans' floats behind the breakwater - it's a bit busy too but sometimes an end spot will free up.
I don't think we've ever been totally skunked looking for overnight moorage at either of these two places. We have had to raft up on occasion.
Sorry, we've not been to the marina at the end of the bay, but the Seattle YC has taken up a 25% holding there as an outstation. Some details here:
Seattle Yacht Club - Ganges