My experience with Latino guys in Central and South America is that straight Latinos often have a different opinion about what is gay or straight. As log as they are the active partner then it is straight. I have even been in groups of straight guys in Mexico, Guatemala and Argentina where one guy will boast to the others about how some gay guy really wanted his dick and how he gave it to him, plowing his ass until he couldn't take anymore.
What you describe Juanjo is exactly the kind of models and scenes that I love on Broke Straight Boys, when a very straight identifying guy is willing to fuck and get sucked because in his mind, "that ain't gay". Yes, I agree with many that it is an erroneous concept, but that attitude does exist, and I get very turned on by that type of "straight" guy with that mindset. It would be very unlikely to find a straight guy in the US who would do that.
However straight guys in the US are often willing to fool around. It always depends on the circumstances. They do not want their friends to know. They do not want anyone to indicate in any fashion that they are gay. They often will have some little issue - they won't kiss but you can screw them. You can't touch their ass but they will suck your dick. The variations are many and depend on the people involved.
Indeed I have been with many younger guys who fit that category, with me seeking out those who enjoy receiving oral, but nothing else. That is my fantasy or fetish.