From Berlin and Brandenburg the "Brandenburg-Ticket" is the best choice: 5 people from 9am on in all regional and interregional trains and Underground and Suburban in Berlin for 29€ (ticket machine). On the weekend valid before 9am. The ticket is valid until Neustrelitz even if it's already in Mecklenburg.
Also from Hamburg you can use the train with the Mecklenburg-Vorpommern-Ticket and the Schleswig-Holstein-Ticket. From other corners of Germany you can use the "Quer-durchs-Land-Ticket".
From Neustrelitz you can use shuttle busses (3,50€):
Thursday: 2pm-11pm every full hour
Friday: 11:00am/ 1pm / 3pm / 5pm / 8pm
The shuttle busses wait for the arrival of the trains from Berlin and Hamburg which are supposed to arrive every full hour even if they are late.
Taxis from Neustrelitz to at.tension cost around 35,- bis 45,-€, depending how good your negotiation skills are.
The departure times will be available on our Infopoints on-site.