A bit cold now, April-May is best and very hot in summer months.
Calico has lots of fun trails, and some difficult ones (Odessa Cyn...).
Plenty of mines to explore the absolute best is the Bismarck Mine on top Northwest of the hills (red star). Search for the entry at the top, multi level mine below, bring flashlights.
A tricky drive through arch that has claimed a few FJ rear windows (red eclipse). And some shooting areas.
Dirtopia's map with accurate difficulty of trails and shows location of Bismarck mine.
Highlighted route is easy to very mild moderate hitting some highlights. The diamond trails are challenging and worthy of respect.
Steve know's much more about the area...