Book a tour with an operator in San Pedro. You will have a MUCH nicer day - more time spent on the good stuff, and also the boat rides will be made part of the fun instead of a time-wasting, crowded bus-ride.
Really - the island based tours to the mainland are worth EVERY penny - there is no comparison.
Have your hotel book you - they will know who is going on what day and what you can expect.
ENJOY !!!