Yes you will have no issues, the differences are quite minor. And they will appreciate you speaking their language even if it is Castillian!
One big difference (according to my Cliffs notes Spanish
) is that Mexican spanish doesn't have the "th" sound in certain words. So in Mexico, siento 'I feel' and ciento '100' sound the same. In Spain the first sound is an [s] in the 'feel' word but a "th" in '100'.