I wasn't aware there were good hiking spots in Vegas until I had lived there for awhile. Mt. Charleston would often come up in discussion of the spots to try.
Cathedral Rock is a relatively easy to moderate hike for a great view of Mt. Charleston and the surrounding desert at the top. It's about 3 miles round trip to the peak. The hike starts at a steep pace and then flattens out for awhile, then becomes steep for a short final stretch.
Be sure to check the weather before attempting the hike. Desert weather can be volatile.