There is no bus schedule, but they move along the main roads very frequently - the wait is rarely more than a few minutes. They do stop running fairly early in the evening. And there are some areas of the island they don't service very well. Having said that, I've been visiting SXM for twenty years now (really going to miss it this January!) And rarely rent a car very often now. I stay at the RI and can walk to lots of places in Maho. I'm not much of a night owl and will use a taxi on those evening when I will be out later than the buses run. I will occasionally rent a car for a day or so. That works for me, but everyone is different.