Do we have to know lots of Spanish to get by, and to have fun?

No Way!!!  It certainly helps and makes the experience richer and more fun, but you definitely don't have to know a lot of Spanish. You can always get what you need to enjoy your Troncones experience using English. 

The vast majority of Mexicans and locals in this area are extremely nice. They're happy that you're visiting and are happy to help you enjoy your stay. We encourage you to give Spanish a try, though. The people appreciate it when you make the effort.