I suggest starting with cassette tapes in your car where words and phrases are spoken in English, then multiple times in Spanish (available at many book stores and on the net). Listen to each tape over and over again until you know it cold before going on to the next tape.
When you start to listen to the more advanced tapes that include past and present tenses, try watching Spanish soap operas and listening to Spanish radio stations. Then find a pen pal that knows English and Spanish well. Write 1 or 2 page letters in English, then translate them to Spanish. Send both versions to your friend and ask for corrections. After a while, you'll be writing them directly in Spanish. Reading and writing the language does wonders vs. just listening and speaking.
Then make your trip. It will be much more productive. Keep your new language skills fine tuned with frequent phone calls to someone that speaks Spanish (that you meet on your trip). In addition to picking up a Spanish to English dictionary, buy the book "501 Spanish verbs" (Kendris, ISBN 0-8120-9282-1). It has 501 verbs fully conjugated every which way possible and will be a valuable resource. Also pick up "The Oxford Minireference Spanish Grammer". It explains lots about the way Spanish is spoken that never seems to get explained in other courses.
Jim Hinsch JimHinsch@CSI.COM