How fast is it possible to learn a complete language?

I need to learn spanish because I am spending the summer in Spain, which is in about 5 months. I know basics like colors, certain expressions, days and months. Will I be able to learn it in time? I also have the advantage of having 2 native Spaniards and someone from El Salvador, all fluent in spanish. Can I swing it? Also any good workbook titles or programs I should try?