Montreal trained at Jackie Robinson Ballpark in Daytona, FL during the 1970s, so I assume that's what we see behind Ross. The park's Wikipedia page claims Brooklyn moved their spring training home to Daytona in 1947 after Jacksonville denied the Dodgers permission to play a 1946 pre-season game with Robinson on their AAA roster. (The team moved further south in 1948, building Dodgertown in Vero Beach.)
1979 marked the last vintage Hostess set published on their snack cake boxes and contained 50 three-card panels (for 150 players total), six of which are single-printed and listed below. (Thanks to the Super70s set checklist for the details.)
Value: Hostess cards often show up like Mr. Grimsley, with odd edges left by young scissors, and even snack stains. They rarely cost more than a dollar or two.
Fakes / reprints: Haven't seen any in the marketplace.