I have lived in Rostock for over 10 years (I transplanted myself from the otherside of the planet for work). In those 10+ plus years I have visited, as a solo traveller, almost every village, town and city in the state of Mecklenberg-Vorpommern, by local transport, cycling and even walking, and I have always felt safw. If you do not speak German, you will always find someone who can help. The city of Rostock is beautiful, and you are never far from the beach. There are always events on, and a good social scene. Tipps: (1) when you are on the street, in parks, on the beach, in shops, at events or restaurants, greet people with "Moin". Its how many locals greet each other, and it may win them over. (2) hire a bike, and head over to the beachbetween Marktgrafenheide and Graal Muritz. They are mostly empty and you can relax and enjoy yourself. Bring food ans drink with you. Its FKK (nude beaches) as well. Not compulsory, but you should know.