There's a nice loop in Prescott around Lynx lake, which is not too hard, but a nice ride nonetheless. Most of it is singletrack through the forest, about 15 miles. It takes about 2.5-3 hours.
I haven't been, but I hear that Granite Basin loops are also a lot of fun, with something to offer for various skill levels. You might look into that also.
Let me know if you want more details, or ask any questions.