You won't be able to cook at Cobalt Coast unless you rent one of the cottages so consider a condo at their sister property - Lighthouse Point instead. It's the other Divetech shore dive as well and they shuttle you as needed between the facilities for boat dives. Also marginally closer to the
Foster's IGA market in West Bay.
Grand Cayman Scuba Diving Divetech.com - Lighthouse Point Condos
Between the two locations, the other really good shore dive is at
Turtle Reef. Add a couple of boat dives with Divetech and drive down to Sunset House one afternoon for their shore dives/lunch at My Bar. Being a photographer you may enjoy the Cathy Church Photo Gallery/retail camera shop also. Cathy's often there - ask her to sign a print. And plan on an hour talking photography with her afterwards - nice lady.
A shallow dive further south just past Sunset House is Smith's Cove - rent tanks at Eden Rock or Diver's Supply in town - Divetech likely won't let you remove theirs from the property. Also there can be 4-5 cruise ships in Georgetown Harbor so if any of those sites are of interest consult the
cruise schedule and plan to go later in the afternoon - the cruise port is about 500' from Eden Rock. A couple of these no longer exist (Seaview is condos now) but here's most of the options:
Scuba Shore Diving Site Listing for: Cayman Islands, Caribbean
Since you mentioned Grand Turk - the quirk on Grand Cayman is no food store is open on Sunday. There is a Foster's market as you leave the airport though that's open pretty late on Sat. night.
We'd like nice shore diving and occasional boat diving. So far Bonaire is at the top of the list...Ideally we'd like a condo or rental on a beach.
Curacao should be instead. Unlike Bonaire they actually have beaches. Most are also shore dives with on-site dive facilities. The condos though typically aren't beach front as much as surrounding it on low cliffs so you get the breeeze and the view. Once you leave town things get real quiet real fast also.
There's quite a few condo complexes on named dive sites with their own dive operators also. If there's a downside to Curacao it's that the driving distances between sites are a little farther than Bonaire. One advantage is that just about every beach is a dive site. There's even escorted shore dive options, Bas Harts, the Dive Bus, Atlantis Diving - the latter two pick up anywhere in town. Their version of Buddy Dive's drive-thru is Relaxed Guided Dives - on the road west from town so pretty convenient for that area.
The upside for spending a month there is the non-dive activities - I agree with Kharon, unless you're easily amused Bonaire woould be boring by then. Since Curacao actually has a downtown (world famous shops) nightlife, casinos, some excellent restaurants - many beachfront, old historical sites, excellent beaches, Crhistoffel Park, etc. a month there would be about right to see it all.
Two miles north of downtown is the Piscadera Bay area - rented a condo there once - it's pretty quiet at night. As you move farther west (or east) outside of town, crowds aren't going to be a problem at all. Lack of amenities more likely - the restaurant count goes way down as you move west. And food stores are non-existent much west of the airport area. What a lot of people do is stop at Centrum or CostULess - both just south of the airport - before driving out. Centrum sells $1 styro boxes and ice for perishables. The airport to Westpunt is about a 45min. drive - to the east end about 30.
Some places to look at in the west - by distance from town. Blue Bay, Coral Estates, Lagoon Blou, Marazul, or villas you can find on vrbo.com in the Westpunt area. All are either on house reefs or close to one. I know most of these sites west of town - if you have any questions about what's nearby - I'm not so good with east except for the Tugboat - there's nothing much near it. Caracasbaai seemed like a nicer, quieter area also as we drove thru.
http://shorediving.com/Earth/ABC/Curacao/index.htm
www.curacao.com list options for just about everything. It seems like a much better option for your month. If you miss Bonaire - split your time - Insel Air offers $60 (one way) flights mid-week on off days occasionally - or did b4 DAE went bankrupt.