Belize is nice and safety has never meen an issue for me. There's a little nightlife in San Pedro (SP), but nothing to write home about. You can take the water taxi from Belize City to San Pedro, Ambergris Caye. Get a taxi at the airport to the Marine Terminal and grab the water taxi from there. To go on to Corozal, you can take the Thunderbolt. Unless I'm mistaken, you'll have to take a taxi to the Mexican border between Corozal and Chetumal, but you can get a bus from there to anywhere in Mexico, including Cancun for the nightlife.