Every excursion is different. I would not plan on having a secure lock up for valuables. The best place to ask the question is with the tour provider.
Top 25 Contributor
Which port? Which excursion?
No two ports or excursions will have the same facilities. Lockers are not available in most of the excursions we have been on. You are responsible for what you carry. On some excursions, if it is a conducted tour, your bus driver will allow you to leave stuff on the bus because they will stay back on the bus. As far as changing is concerned, there will be some sort of restroom to change but it may not be clean or large enough to change.
Number One Contributor