I'm not familiar w/ the Playa Grande (must be pretty new). Amigos Del Mar is the nearest shop to the Solmar & the Finisterra. I have not been their customer, but they have great reviews from SB members, and the last time we were in Cabo, their boat also looked nice. They have one of the larger shops.
On the marina, the former "Plaza Las Glorias" (changed their name, but I'm sure all the locals know Plaza Las Glorias) has several dive shops. I've used Baja Dive and Land's End Divers. I would recommend Land's End Divers.
General advice: (1) avoid diving on the day(s) that the cruise ship(s) visit. Rent a car & go somewhere else
(2) just about all the Cabo dive sites are within a few minutes' boat ride from the marina. There's an advanced open ocean sea mount trip which is a long way, that they do only if there's sufficient people. I wouldn't go diving Bahia Chilena or Bahia Santa Maria, unless you do those as shore dives (someone drives you & your gear there, etc.) but I would definitely go to the beach there. (3) if you get a group trip (organized by a local dive shop) to Cabo Pulmo, go. If not, rent a car, and plan to do it yourself. Be sure to carry lots of cash, as the Cabo Pulmo op does not have a credit card machine. (4) eat at Solomon's Landing (on the marina). (5) Avoid the time share sharks
If you look at my photo gallery here (I don't know how to get to it, but I know it's there
), you'll see photos + 1 album. Don't look at the album, look at the photos. All the photos (except for the album) are from diving in Cabo. These were pre-SB-album capability. The album is a recent Puerto Vallarta trip.