Galen wrote
Are there any "warm water" turtles? I stuck a thermometer in
the pond water and it said 88. Sounds pretty warm to me. Seems like
I
might need a low fence (how high can turtles jump?) around the pond.
Are
they real territorial and aggressive, or will they live in harmony in
fairly large groups?

There are lots of turtles in your neck of the woods.
http://plants.ifas.ufl.edu/guide/turtles.html
You can get free turtles by contacting a turtle rehabber.
These nice people take in ill and sick and unwanted turtles
and fix them up. Vets and pet stores usually know where
to find them. A google search might turn some up also.

Turtles can't jump but they can climb and wriggle thru places
you think they wouldn't be able to go.
Most turtles live together fine. Sliders will stack up on each
other to bask. I think snappers are more solitary.

Most importantly they need safe places to baskin the sun. They like
warm temps and spend the winter (depending on how cold
they get) at the bottom of the pond or under a log, depending
on the species. They are temperature driven - it gets cold they
slooooow down.

k :-)