I want to see if this is common & why?

Some background. As babies, my brothers and I had a Spanish speaking, live-in Nanny for 3 years. I do not speak, & have not studied Spanish. I cannot participate in spanish conversations. I doubt our Nanny was teaching babies extensive Spanish though she had pet names etc.

Years ago I worked with Hispanic coworkers who spoke Spanish & English. One day we were rushing through a project & though distracted, I responded to a joke one of the guys was telling. Everyone stopped & said "You understood that?" I had been focusing on our task, but heard the joke in English (& responded in English). They insisted he told the joke in Spanish

The 2nd time this happened I was being robbed. I was with 2 friends & we were held up at gunpoint. I was in shock but I heard the robbers say 'give me the keys" repeatedly. To this day my friends say they were speaking Spanish but I heard English

Anyone have similar experiences and know exactly why?

In Texas a large percentage of Americans who are of Mexican ancestry are non Spanish speaking,and most are highly assimilated in the sence that English is their first language,and they do not hold on to any Mexican cultural ancestral values.I see this more often in the 4th and 5th generation USA born Mexican American peoples.

I would like to know what people who speak Latin American Spanish think of people who know or are learning "Castilian" or "Spain" Spanish. I have been learning how to speak spanish for a few weeks now with Rosetta Stone software. I am learning so that I can travel to Spain. I would like to try some of my spanish at work with some of spanish speaking co-workers but I don't want to sound like an idiot speaking Castilion when they are from Mexico. I don't want to screw up and make my "s"s sound like a "th" and sound like I have a lisp or something.