Spanish immersion, staying with local famliy

Looking for a Spanish immersion course next summer for our 2 sons, (22 and 21 years old) They have very limited knowledge of Spanish, like to house them separately, so they have to speak Spanish, with local family. Both are high achieving, self starters that will be scouting the country for us, for possible retirement/ investment options. Also looking for graduate colleges for the boys for the school year starting fall semester 2014. Any information will be greatly appreciated. Caren