Lobsterfest weekend is one of the busiest of the year, it ranks right up there with Easter weekend, Christmas and New Year. I don't think the prices change or go up for Lobsterfest, they stay the same all summer. You are coming in low season, so will get the best rates., However, you may not get additional discounts on account of how busy it is that weekend. Caye Caulker has lots of day trippers from San Pedro and weekenders from Belize City for Lobsterfest.