Beware.
The grounds are absolutely beautiful. Birders, bring binoculars. The view is wonderful, and the staff are helpful in the Guatemalan style.
However: located next door to the San Buenaventura are the three towers of the "Riviera Atitlan" hotel, and if the Riviera Atitlan decides to host an exceptionally loud church retreat, then not only will you have wasted your money, but you will also be desperate for sleep, peace, and quiet - and this AFTER coming to a place that promises tranquility.
We brought our family to the San Buenaventura for a few days of vacation, and an hour after we arrived, a live band started warming up next door. We were out on the dock, and we had to raise our voices to be heard. The group next door sang, preached (yelled), and played games until late into the night, and then began again - band at full volume! - at FIVE-SOMETHING IN THE MORNING. It was dark. We were tired. It woke us all up. The kids were miserable.
The group next door continued all day, and our only escape from the misery was to the nature preserve across the street (highly recommended). We were kept up until 3 that night, and shaken out of bed once again at 5:20. Now I know why governments torture enemy soldiers with relentless noise. It's absolutely wretched.
Of course we had talked with members of the staff at various times, asking if there was anything they could do. They certainly tried, knowing how ridiculous the noise level was, but there really wasn't anything they could do. If there's a noise ordinance, I can't imagine anyone (say, the police) would actually do anything about it. The managers of the hotel next door (where the noise was coming from) had no incentive to shut it down, so they didn't.
All of which we understood. Things like this happen sometimes. But after paying $500+ for two nights, I might have expected better treatment from the management. The man at the desk asked if everything had been allright, and of course I had to tell him it hadn't (he knew anyway, as he had called the neighboring hotel the day before). I told him I'd prefer to pay for just one night - we'd cover our expenses, but wouldn't be paying quite so much for such a wretched experience. Besides, the San Buenaventura was almost empty that weekend, so we hadn't taken anyone else's spot. He called the owner, and once she found out our credit card had already been run (during check-in), that was the end of the conversation!! That, apparently, was all she needed to know. I asked to speak with her myself, and when I did, I was given long explanations of why the noise wasn't the San Buenaventura's fault (which is absolutely true), and how she just couldn't charge me anything less than full price for my stay. Not even a few bucks? Really? I came for a vacation and didn't even get to SLEEP??
I was told that the owner would discuss the situation with the owner of the Riviera Atitlan and would be in contact with me (but would under no circumstances reduce the charges to my bill). It's been a few weeks, and I've heard nothing. The grounds are indeed lovely, as is the unbelievable lake surrounding them. It's a great place to take a family with kids - plenty of room, kid-friendly staff, etc. But if you're looking for a quiet stay, do yourself a favor and make sure nobody's staying in those three green high-rises, or you're in for a very loud stay, and a hotel whose primary concern is whether or not your credit card has already been charged.