Onan;
Since you are in Dallas, I will answer <G>... In the US, class A is the only place where VFR is not allowed (you can get a waiver though.). Every other bit of airspace you can get into VFR. Class B needs a specific clearance and then class C you have to have communications with the controlling facility and have not been told to remain clear.
regards
Scott H. Voigt
NATCA Southwest Region
Safety Chairman
Fort Worth ARTCC