So, it seems that Hidden Pond is the place that most folks want to go. Works for me.
Which trail head would everyone want to hike in from? There are several options...Pat's Island (the perennial favorite) at 3.5 miles, Juniper Springs (fee to park) at 5.3 miles, Hopkins Prairie (two of 'em) at 4.5 and 5 miles, Farles Campground at 14.7 miles, Salt Springs (fee to park) at 15.2 miles, and US 19 at 19.7 miles.
Water sources are...difficult (we'll either need to stop at Juniper and pay the $5 day use fee to get water from them or carry ~14 miles of water, about 4.5L per person in the kind of terrain we're going to be moving through) if we're south of Juniper Springs. I'm not sure about north of Pat's Island; I've never been that way.
However, according to the data book (which is occasionally wrong, but since it's talking about established campsites this time I'm inclined to believe it), there's water at Hopkins Prairie and there will be some at Salt Springs (it's an established campground, so there should be running water), so the longest stretch through there should be ~10 miles or just a wee bit over 3L.