B. M. Bower 
Gringos 

We have two cowboys who have gone to the gold fields and had the good fortune to make a bundle from their mine. Dade Hunter is the quieter, steady one; Jack Allen is the firebrand who is always getting into trouble. They decide to spend the winter in a very young and raw San Francisco. Jack loves the gambling life there, but Dade gets tired of it all pretty quickly and rides out exploring, ending up in Palo Alto, where he makes friends with Don Andres, the Spanish owner of a large hacienda. He returns and tries to get Jack to go out to the ranch also, but he refuses. He will soon wish he had not been so stubborn! (Goodreads)