The most stunning beach on the Cape is Race Point Beach, an eight-mile stretch of sand with crashing waves and sport fishing in the breakers, dominated by its eponymous lighthouse. More sheltered is Herring Cove Beach, a peaceful swath on the bay side separated into straight, lesbian, and gay areas. The beach was once the province of nude sunbathers; however rangers have since quashed the practice, so disrobe at your own risk.
Both beaches are accessible by public bus. Shuttles leave Macmillan Wharf for Race Point every 40 minutes 7 a.m.–8 p.m. and for Herring Cove every 20 minutes 9 a.m.–a half-hour before sunset. To get to Race Point by bike, head down Conwell Street to Race Point Road, where a bike path parallels the roadway. For Herring Cove, cyclists have two options: they can fight the traffic along Route 6, or take the longer but nicer ride along the bike path through the Province Lands [1]. Pick up the trail at the Beech Forest Parking Area off of Race Point Road.
Links:
[1] http://www.moon.com/destinations/new-england/massachusetts/cape-cod/provincetown/recreation/province-lands