Depends on where you are and whatcha need. Down in the Sandy Eggo, dive shops aren't what they used to be; both in quality as well as service/location. OE (Ocean Enterprises) is the big seabass in town but that also comes with marginal staff and location (they're in the Kearny Mesa area). A new(ish) shop in town is Beyond Land Adventures (BLA), they are located in the Midway district by the Sports Arena, just down the street from the old Sports Chalet. Speaking of Sports Chalet, BLA bought their fill station and bank so it's a solid system, albeit hot fills compared to OE which uses a dunk tank. For technical fills like O2, unfortunately the place in town is a shop I wouldn't recommend to my worst enemy in Sorrento Valley. The owners are d-bags, complete ballz for customer service. If you want NITROX OE has it, 32ish banked through a membrane system.
Shops have really cut back and fills are somewhat a PITA to get, plus the diving right now is crap. Hopefully this gets better but from what I'm seeing at the beach, people just don't get the distancing thing and my marbles are betting on RED that we will have a round 2 of closures... soon. Some states are nearly there as I write this.