Site visited just recently (July 2013). Easy accesible from Gori bus station by local marszrutka (small bus), last bus stop is just besides the bridge in Uplistsikhe village, from where there is just 500 meters to the Uplistsikhe Cave Town. Entrance fee for adults is 3 Lari (1.8 USD), for students and children it is 1 Lari.
Comparing to Vardzia, Uplistsikhe Cave Town is relatively small, walking through caves cut out of the rock should not take longer than 2 hours. Some of the caves are remarkably decorated with carvings (do not miss Tamara's palace and single-pillar cave).
Transport back to Gori - same bus stop, although the returning course may take some time. The whole trip may take 3-4 hours depending on local transport.