Shouting would encroach on private property.
Shouting as in screaming? That's your first amendment right
Disturbing the peace is the typical charge. In most all US jurisdictions it abridges the 1st amendment.
There are lots of bad laws. Florida has more than its share.
Florida has laws we libertarian types would not like in our freewheeling communities because it is full of old people.
When you are old, the homeless are more disturbing to your peace, which is reflected in their local regulations.
Old folks can more easily break a hip if a crazy/grumpy/drunk/high/entitled homeless person shoves them.
Old folk's weaker immune systems are more likely to be effected by pathogens transmitted by the homeless.
Old folks are more likely to have visiting family who wish to use a park that is not filled with feeding/crapping/camping/begging/stealing/fighting/disturbed homeless people.
As a libertarian, I'm sure you favor local control and realize that what works for healthy 20/30/40 somethings in San Francisco or Seattle doesn't necessarily work for the 60+ senior citizens of Florida.
A public park is subject to the tragedy of commons if the those who pay for its upkeep (IE local taxpayers) have no authority in its administration. Yes, in our ideal Libertopia there would be no public parks and all communities would only have one law (Crowley's "Do as thou whilt..." maxim), but you are intelligent enough to see my point stands regardless.
The bridge to Libertopia is build with stones of local control and the mortar of federalism.
(I changed the original "bricks" in the previous sentence to "stones" because bricks are all the same size but stones are organic and nonuniform).