Pete, i completely agree with you - i find reading spanish much much easier compared to listening to it. Although - here's another exception word which my spanish teacher told me yesterday and could get you in a bit of a muddle! 'constipado' in spanish does not mean you're constipated but that you have a cold so going to the doctor with that one could be interesting!
Anyway, Christie, before i went to chile on my gap year i spoke barely any spanish but after living there for two months i felt really confident getting around on my own which was really rewarding. My vocabulary really improved just by keeping my eyes open and reading everything around me - road signs, menus, magazines... Of course having a bit of the language before you go helps but the more you interact with local people the more you'll learn and the more you'll enjoy yourself. Also people are much more receptive and friendly if you make a little bit of effort. This year I'm making the most of the inexpensive spanish lessons which my university offer and now i'm getting to grips with the grammar i really want to go back to south america and get talking! Have a wonderful trip - spain is a beautiful and vibrant country.