You can get 4'x8' sheets of clear Lexan for like $12 or $15. They make many kinds of lexan. You may want to get a lightly tinetd type in Georiga. I think the polycarbonate is one of the more expensive. You may want to avoid that type. Price also depends on the thickness.
You may check with builder supply places to see what type of aluminum frames they offer or look for Florida room kits on the net. You need to hold the plexiglass in place with something.
You must plan to have some windows that open in your design. Otherwise, it will get too hot to use. You can install cheep bamboo type miniblinds for shade and privacy.
I would stay away from electric or plumming at least in the beginning. I think its easier to pass building code for an enclosed porch type of deal.
Make sure you have a well thought out plan before you start.