The well protected beach of Port Erin can provide some good quality beach break waves in big SW swells. SW winds are offshore. I have kite-mountain-boarded on the hard packed sands of the beach as well, but the high hills surrounding the beach tend to make the winds gusty and unpredictable. The hills do however provide some spectacular views and pleasant walks. There is a surf/windsurf shop on the beach and all amenities are available in the town. You can park all along the beach.
The walk to Bradda Head which overlooks Port Erin is nice, or for the less energetic a stroll around the southern edge of the beach past the small harbour and marine research station is less strenuous.