Time Trials is now known as HPDE.These events aren't time tirals as I understand them since they are not at a track. I think time trial is essentially an autocross but at a racetrack.
Yes you have to be a PCA member to run. But the OCR region allows non porsches to run, and the SD region does not, unfortunately.
I am a pca member (have been for 5-6 years now) because I had a boxster and cayenne.
Sweet what are you driving, exige, elise???