This depends on your commitment and eagerness to learn the language. At least, you'll be a better prepared for your travels. If you want to devote more time, you'll have a greater command of the Spanish language. As with other things in life, you'll get out of the experience what you invest. If you are combining education with travel, make sure you cover the bases.
Many schools offer home stays with local families.
You can also arrange your own lodging or choose to live in an apartment or hotel. Consult a guidebook to get a good idea of what lodging typically costs. The best bet is to select a school on prior recommendations. A school's word of mouth reputation is worth more than all of the advertising in the world. If you have any doubts, don't commit yourself to more than a week of classes.