Is it possible to visit the Terracotta Warriors independently or must it be done with a guide?

Yes, it's ok for you to tour around the scenic area by yourself. However, if you have limited time and won't miss any major scenic spots inside, you'd better find a tour guide. TravelChinaGuide is highly recommended. This travel agency wins high popularity among foreign tourists. If interested, their contacy information is traveltravelchinaguide.com.