If you're in eastern central Florida, most likely in the event your municipal source becomes compromised the state and county will provide an alternative supply, up to and including having potable water trucked in by tankers etc. You should probably keep a 7 day supply of water on hand anyways, if you have room to stock it.

I wouldn't recommend using any surface water source here in east central Florida, especially during/after a hurricane or other flood related incident, as all surface waterways will quite likely be contaminated with a whole list of organic and chemical hazards that would require some serious processing effort to clean up. If you must, I would suggest trying to make use of groundwater sources instead, as that might afford you some isolation/filtration from the surface contamination, but you would still want to at least boil it, filter it, or chemically treat it, or a combination thereof. There are springs here and there all over central Florida that would make much more reliable sources to draw from. Barring that, find someone nearby if you can with a nice deep well that is prepared and has a means of extracting the water in the event the grid goes down. It might take some investigation, but it is well worth it if you are at all concerned you might need an alternative source, which it sounds like you are.

Florida is the epitome of the cliche "Water, water everywhere, and not a drop to drink". Bear Grylls' little escapade in the everglades was extremely risky, he is really lucky he didn't get a nasty bug the way he went about his business. Les wasn't so lucky, and the Georgia swamp water gave him a parastitic infection he dealt with for over a year afterwards. All raw surface water here is pretty much a no-no.