Blunt-nosed leopard lizards live in arid areas of central California. They can typically be found in open, flat areas with few plants.
Im not exactly sure how long blunt-nosed leopard lizards have been around, but we can make an educated guess based on some facts.
(1) Blunt-nosed leopard lizards occur only in the San Joaquin Valley, and are thought to have evolved there from other desert leopard lizards. This makes them what scientists call endemic species.
(2) They live in arid (desert) environments.
(3) The San Joaquin Valley for millions of years was under a vast ocean. Only in the past 2 million years, after being cut off from the ocean through geologic events, did it dry out and become desert. This tells us that the environment that they need to survive, in the place where they evolved, only came into being, at most, 2 million years ago. Based on these three observations, we can conclude that blunt-nosed leopard lizards have probably not been around for more than 2 million years.

By the way, the taxonomic name of blunt nosed leopard lizards was changed in 1993 from Gambelia silus to Gambelia sila. This has to do with some boring conventions of Latin grammar. It may help you if you want to do more research on this species to have the updated scientific name.