What do “Latin American” Spanish speakers think of people who speak “Castilian Spanish”?

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.