I can't say much about the Rutledge Inn; I'm sure I've driven past it, but don't have much reason to stay in hotels in my back yard.
As for diving/snorkeling: General concensus is that there is little to no beach diving in Palm Beach County. There just isn't any reef close enough to shore. Singer Island has several beaches that offer some decent snorkeling, however.
MacArthur Park is just to the north. I's a $3 entrance fee; be prepared to hike. The access bridge takes you over the intracoastal, and the coral head is another 100 yards north once you hit the beach. And it is A coral head. One. It's enjoyable for bringing novice snorkelers. The park also offers kayak tours, etc. By the looks of the website, it has now reopened from the hurricanes, though the last time I drove past it was still closed.
Ocean Reef Park is also on Singer Island. I have never snorkelled it specifically, but there are a number of visible rocky upcroppings, etc.
As for diving,
Pura Vida I knows departs directly from Singer Island, but I have never actually used them.
The majority of dive boats are docked in the Riviera Beach marina, a five minute drive south. These include the
Narcosis and
Diving Solutions, both well regarded here on the board.
Dive Shops nearby:
Force-E is just over the Blue Heron bridge on the south side of the road; they are the only dive shop in the area that offer Nitrox fills or rentals, if you have the need. They also coordinate dive trips, if you'd like to just go through them. Gear options are limited, but the guys are the best.
Seapro is just up the road @ a mile, but I've never even been in the store, so can't tell you much about them.
Let us know when you're in town and some of the Conchs will probably set up a trip! We have a habit of that.....
