The group I travel with stays at Lion's Dive Club. I would say the accommodations are adequate, though not great, and the folks at the in-house dive center (BonBini) are good (especially Mañanita, who found me my orange seahorse!). The restaurant there is good and you can walk next door to Captain Don's for dinner as well. As far as theft goes, we never had any trouble on our last trip, though you are constantly warned never to leave anything in the car you don't want stolen (and for Pete's sake, leave them parked with the windows down and nothing in plain sight) and not to leave anything drying overnight on your balcony (this recommendation, in particular, is tough for divers and was never followed despite the fact that many of the sliding screen doors had the corners peeled up). When theft occurs, they'll take whatever you leave in the car, no matter how little value you ascribe to it (T-shirts, old ratty tennis shoes, torn dive bags). Perhaps to combat this, many of the rental trucks now come with lockable bed boxes. That appears to be at least some deterrant. Whatever you do, accept the rental company's insurance on the car. The group had one person a couple years ago get their car dented -- the rental company wouldn't let them off the island until they paid an outrageous price to fix it. The next year, someone had a window smashed (they left a new pair of Nikes in plain view in a locked car). The rental folks were drooling all over themselves as they added up the cost but had to back off when told that their insurance had been accepted when the vehicle was rented!
Mike