I own a place in Marathon and spend several weeks a year down there.  The rest of the time, my boat is in a hoist in northern FL.  I also leave the boat in the water.  Depending on the time of year, slime starts to grow after 4-5 days and harder crusty stuff after maybe 10 days.  The slime comes off easily with a wash mit.  Good excuse to put on a snorkel.  If you leave it in for more than about 10 days w/o cleaning, it's harder to remove and gets progressively worse.  If you're only in for 7 days, I seriously doubt anything will attach itself that won't easily be removed by a car wash pressure cleaner.  Hope this helps.