I always, always, always get a locker. Sometimes I just don't have everything with me that I need and it's just too much to take that hike back to the hotel. I think it's worth it, in the scheme of what else you spend money on while you are there. Plus it means I can take my tripod into the park in the morning and not have to worry about it until I need it at night, lol. Or if I'd like to get ride of the heavy camera for a short while.
And yup, there is a locker place in the middle of Main Street - right across the way from the Carnation Cafe in that little 'side street'.