If you're usually riding by yourself and are very confident you'll never have to carry more than two people, a first-gen Insight is about as stingy as you can hope for. Some guys here push them over 100mpg in summer months.
There's also a couple of modded Civics that go past 70mpg, I'm not sure how they do that. I am in awe of those guys,
Donkey CRX,
OG VX and my personal favorite
Gasoline Fumes, who is banging down numbers that would look great on my Hybrid, but he's doing it with a 25-year-old minivan.
So if you have your heart set on a hybrid that's great, but it's clearly not the only path to great mileage numbers.
Speaking from my experience I'm going to recommend against the Civic Hybrid. I like mine well enough but the IMA battery is a proven weak point. It's more the great depth of experience in the commentariat that has kept mine in good nick than anything else; I have leaned on the wisdom of others and have gotten my IMA battery back into good working order.
I will say this: not having a timing belt in the HCH is VERY nice. I think all models of Prius from 2001-2012 also use a chain. One less thing to worry about.
There's an '06 Prius on the Tampa Bay Craigslist pages right now, $4000 and looks pretty good, but only one picture and sparse description.
If you're willing to go very old school, there's also a '90 Geo Metro 5-door going for only $1800, that would leave a lot of scratch in your car budget for, for instance, swapping the power-robbing automatic for a 5-speed. That Metro is described as having only 65K miles and from the pictures looks surprisingly good. They don't have much occasion to salt their roads in Florida, most of the undercarriage might even still be there.
Crap, I might need to run down to Florida.