One of the best sources for local knowledge and the ins-and-outs of the area and also for adventure activities (diving, canyoning, et cetera) is the proprietor of Adventure Diveshop, Mike Feeney, right on the main Rizal Avenue. He is quite insightful on where to stay, hang-out and dive and not get gouged at tourist rates.

 However, if you're looking for information before taking off, you should visit the big Info site about Dumaguete  or read up about the city on Wikipedia

Dumaguete is a good stopping point for other locations nearby, Mabinay caves are pretty cool and some are quite advanced, really nice people up in the mountains.