No. Common courtesy would be to say "hi there, hows it going"
There is no reason to "ask permission" to ride any of these trails at any time. Maybe if you were about to drop into a mouth of a one-way double-diamond single track at a bike park, but this is a multi use trail on a weekend where there is uphill traffic, hikers and slower riders to be expected. I know it sucks to have slow riders in front of you when you want to bomb, but that's tough shit, happens to all of us all of the time. They way to deal with it is not to come on this forum and complain that there are pussies in your way and they didn't have any respect to ask if they could go down the trail in front of you first. Should have just waited 5 minutes or just passeed them when it was safe to do so without complaining and not make such a big deal about it. I don't know if the OP is still lurking and reading this or not, but I do hope you reessess your attitude. This kind of "my trail" DH attitude is what makes people dislike mountain bikers in general. Please think about your actions when riding in public trail parks and how they reflect on all of us.
lookie here sport, and listen up to the rest of you that have repeated similar thoughts:
I DO NOT THINK ANYONE NEEDS TO ASK ME PERMISSION TO GO DOWN THE TRAIL. I DON'T THINK I OWN THE TRAIL. I DO THINK THAT IF I AM SITTING AT THE TRAILHEAD ON MY BIKE AND AM A 5 SECOND HELMET SNAP OPERATION AWAY FROM HEADING DOWN, IT IS COMMON COURTESY TO SAY "HEY, ARE YOU GONNA DROP OR IS IT COOL IF I GO DOWN?" THAT'S WHAT I DO FOR OTHERS, THAT'S WHAT I EXPECT IN RETURN FOR MYSELF. I KNOW, I KNOW, THAT SEEMS PRETTY UNREASONABLE.
RE-READ THAT FIRST PART BTW, BECAUSE SOME OF YOU SEEM TO BE HAVING TROUBLE WITH IT: I WAS NOT BLOW APART IN A MESS OF GEAR AND CAMELBAKS AND BIKES ALL OVER THE PLACE, I WAS SEATED ON MY BIKE IN FRONT OF THE TRAILHEAD BUCKLING MY HELMET - AND TO THOSE THAT ARGU'E 'WHY WASNT IT ON ALREADY?', TRY PUSHING A ****ING DOWNHILL BIKE FOR 10 MILES WITH A FULLFACE HELMET AND GOGGLES ON IN 80 DEGREE HEAT. AND NO, I WASN'T SACKED OUT FROM THE EFFORT OF GETTING UP THERE, I WAS LETTING SOME PEOPLE THAT WERE A COUPLE HUNDRED YARDS INTO THE TRAIL CLEAR OUT OF THE WAY IN BOTH CASES, HIKERS IN ONE, SLOW RIDERS IN THE OTHER. HOW LONG AM I SUPPOSED TO SIT AND LET PEOPLE CLEAR OUT/DROP IN IN FRONT OF ME?