The county doesn't have the authority to make it's own firearm regulations. Per state law, a government building with a sign banning concealed carry makes concealed carry unlawful, but the signs do not restrict open carry, in my opinion. While many government organizations respect the law, other organizations like the Sherrif's office do not and will probably require a court case to stop them from trying to regulate guns where they have no authority.
202.3673 - Restricts Concealed carry.
County cannot make regulations:
Note that certain places have gun bans per 202.265 (schools, universities, child care facilities) and there is a law regarding guns in the legislative building.