Can I ride my park board outside the terrain park?

Yes, but with limitations. Park boards handle groomed runs and soft snow adequately for cruising between park laps. They struggle on icy hardpack (poor edge hold), in deep powder (no float), at high speeds (chatter and instability), and on steep terrain (lack of edge grip). If you only own one board and ride the whole mountain, an all-mountain freestyle board is a better choice than a pure park board. Park boards are specialized tools—excellent in their element, compromised everywhere else.