I walk GBF just about every day, but nowhere near where they'd post signs - I'll see if I can find one tomorrow. Our local paper has confirmed the parking charge - IIRC, it was $2 a day or $35 for a year pass.

I have heard nothing about bike tags or speed traps. I can't see the need for either one. I primarily hike the park and have found bikers to be almost universally safe and courteous, and NEMBA's trail and bridge work has been wonderful.