Delurk/Southern California pond questions

Hello all. I live in orange county CA, only about 2 hours north of the
mexican border. So needless to say the climate here is pretty mild,
although we do get some cold winter days/night as low as the mid 30's a
few times a year. I was wondering what fish other than koi would be good
for my climate. The pond I plan on building could be up to 10*20*3 feet
deep, so I could house quite large fishes. After reading the posts about
turtle ponds, I think it might be cool to have a few of those as well.
I've read quite a few previous threads on this NG, and you guys/gals
seem to care and know what you're talking about. Any suggestions would
be great. For the time being I'll have to get by with my 55 gallon
tropical tank, but I enjoy it so much I think bigger would be better.

TIA Josh