I live in Gainesville. We moved here 1.5 years ago from the midwest, though we are both originally from the northeast. Gainesville really sounds like it would fit your criteria perfectly. The cost of living is very reasonable, especially compared to south florida. There is lots of land for sale within driving distance from the city. Though we have all the activities/amenities of a college town, if you drive 10 minutes in any direction it feels rural. We are 2 minutes outside the city limits and have cows within a mile of our house. The city of Gainesville is quite liberal, with some very crunchy people around. Since University of Florida is here (and dominates everything about the town), there are museums and tons of activities for kids. We also have farmer's markets. We don't homeschool, but I know there are homeschoolers here. There is a very active AP group. They are called Gainesville Attachment Parenting (GAP). My kids are a bit older and I am now working full time, so I did not work hard to get connected to them, but I think that would be a key way to find likeminded folks. I think their active Yahoo group is the reason there's not much of a Gainesville presence on this board.
Be warned that the rest of north florida is not liberal at all, and really does feel like the deep south. Another downside is that we are as far from the beach as you can get in FL. Our closest nice beach is 1.5 hours away. After spending the previous 4 years in a landlocked state, this still seems awesome to me, but some folks here complain about it. The summers are long and BRUTAL, but we have as close to seasons as you get down here. We even had a couple trees change color this year! It does freeze, and we have about 4-6 weeks that feel like a mild winter.
Let me know if you have any other questions!