Green Climbers Home, about 6 kilometres south of town, runs guided climbing days and multi-day courses for all levels. They have their own accommodation on site for those who want to spend several days climbing rather than making a daily commute from town. Equipment rental is available and the guides speak good English.
Even if you have no climbing experience, a half-day introductory course is worthwhile. The beginner routes are genuinely manageable and the experience of standing on a karst face with the valley spread below is something you don't forget. Advanced climbers should ask about the harder routes on the cliff faces further from the main areas.