Which Spanish language accent should an American study when learning to speak Spanish?

Castilian? Latin American Spanish? Caribbean Spanish? What accent is best for an American to learn?

Which is better to learn, Castilian Spanish or Latin American Español?

Which is better to learn? Or are they the same, I have a Michel Thomas' Spanish book I think its in Castellano/Castilian. And Rosetta Stone's Latin American Español.

Castilian or español?

I don't know if they're the same

Or Can Castilian speakers be understood if they're speaking to Español speakers and vice versa?

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.

If I have a “Latin American Spanish” learning kit- is that of Mexico/ South America/ where?

I would like to learn the Spanish/ Castilian of Buenos Aires, Argentina, although, for many reasons, the Spanish of Mexico would be good to learn, too.

I have a language kit that purports to be of a "latin american dialect", but as this seems to cover such a vast territory, I have no idea what this means. Please advise & thank you.

Also, I have another similar, albiet slightly different, question going at the same time.