We have found that Yuma would meet most of your requirements. Definitely a younger crowd and the prices are MUCH less than Florida. An easy day trip from here to San Diego or Phoenix with all their cultural activities, yet you live in a rural setting. Lots of history in this area and a multitude of hiking trails.
We are just east of Yuma in Wellton and love the small community atmosphere, yet are in what I would call a 4 star park with lot of amenities and activities that are NOT your typical "blue hair" type of activities. We have a large Canadian population and the median age is probably in the mid to upper 60's. Great area.