There is no such thing as a "solo friendly" site. They will all kill you if given the chance. It might be better phrased as "Dive sites that allow solo diving"?
Non of the State owned sites will allow solo diving and if you get caught you can be permanently banned from access to all State sites, so please don't try them.
There are several other sites that you can dive solo. Little River, Ginnie, Cow, Telford are just a few of them.
Just remember this:
THE ONLY WAY TO DIVE SOLO SAFELY, IS TO MAKE SURE YOU ARE NOT DIVING WITH AN IDIOT !!!
Ginnie only allows solo if you are full cave.