That may be written in the commie code, but in practice, the average Jose on the street is eager to talk with Americans and goes out of his way to do so. The hotel and restaurant workers we met were not so very loyal to Castro. Many slammed him to high heavens in private. Even a good commie propaganda-spouting tour guide we met on a one-day bus tour took us aside when she learned we were Americans and asked us to help her get to New York.
For one thing, the tourist indsutry workers are well aware that foreign hotels are paying Castro $700 or so per worker per month, and Castro "gives" workers a salary of $7 - $12. They're hugely resentful.
See the first hand accounts in my Post 35.
The Cubans are not allowed into the tourist hotels. Even the Cuban husband of that Canadian resort worker was not allowed in the resort. However, the tourists are allowed to go slumming amongst the regular Cubans....up to a point.