You are correct. Training camp is the only time for "open" practices. They usually start the last Sat in July. The actually schedule for ALL the training camp "open practices" will be posted sometime around the first week of July. Times and dates.
Not every practice is OPEN. Usually 3-4 per week once they start. Usually the days before/after Preseason games aren't listed, and there are days built in throughout the month that just are not "open to the public".