My fiance and I just visited Tsali a few weekends ago. She rides a rim-braked hardtail (Trek 4300), and we rode the Right and Left loops at Tsali (marked off for the race course). We both had a blast, and she had no problems with her bike. If you are just looking to have an inexpensive bike so you don't have bring your main bike back and forth - a hardtail would work fine for Tsali. As Luis mentioned, however, there are plenty of trails in the area that you might want to have suspension.