Ron,
Yes, it's the Singlar marina down town Guaymas.
We have only been to the San Carlos maria by car, so can comment with authority on price and facilities.
But I can say that the Guaymas marina is down town, very close to all types of provisioning and shopping. Easy walk to great stores and restaurants. The price was the same as all the other Singlar marinas (see their web site for details). They DO charge extra for water and power, they meter both. We had a slight problem as a boat across from us used our power one day and I had to make sure they took that into account when I paid the bill.
They have a haul out and the yard is very clean and currently is all concrete. We understand they may be expanding and we are not sure about that. It also has a fuel dock. To us, it looks more secure than San Carlos. But It is a commercial area.
I have never been happy about the docks. They are all new, but look at how narrow the fingers are! But then we don't spend a lot of time in the marinas so it's not a big draw back for us.
Hey, if you are passing the Phoenix area on your way down, drop me a PM.
Greg