wow, thank you all for the input!
and looking forward to hearing from wfonseca!
we did a little investigating ourselves..from one source, he really should just get a travel visa and visit (as one of you suggested). Just like other countries, they really don't want to encourage anyone without secure employment or housing to just arrive and try to wing it. My son does speak a little Spanish but would do something like Rosetta Stone to bone up before going, and his friend has taken Spanish from h.s. and into college.
We want to support his decision because, well, this is the time to do those things, when you're 20, and I think exposed to other cultures and such does alot to broaden your vision.
And if he changes his mind in a few days, will let you know