No, you do not need a partner. Every class has frequent rotations so you will have the opportunity to dance with many partners.
It is the unanimous opinion of the best teachers that rotation in group classes without a doubt accelerates the learning process of everyone in the class. When couples choose not to rotate you have a case of the blind leading the blind. More often than not these couples get frustrated and give up after a few lessons! By dancing with various dancers of different levels you will get a better perspective of what a good lead/follow will feel like. In large classes you may rotate through ten partners or so and then jump back to your partner over and over. Start up the rotation a few steps away from your partner and by the time you rotate to each other you will have an idea what you both need. Invariably, beginner couples that stay together get lost together!