My son and I will be doing the Springer Mt to North Carolina Section beginning March 22. We will try to see and get pictures of all Trail Journal posters we see at that time.
Yes there will be more people hiking then as that is the week that the most ThruHikers start the trail. As far as weather goes, I looked up the weather history for Helen Ga and it will be 2 to 3 degs warmer on the average difference between March 10th and March 20th ( not much ). For your Information the Average Temp in Helen, Ga for
March 10 is:
Average High : 61 F
Average Low: 35 F
Record High: 83 F
Record Low: 15 F
For March 20:
Average High : 65 F
Average Low: 38 F
Record High: 80 F
Record Low: 22 F
Remember that this is the Temp in Helen, Ga and not on a Mountain. Expect up to 7 to 10 degs cooler possibly in the evenings if you are up high.
Good Luck on your trip and I hope we get to meet up ( Hike slow 
Jim and James Deane, Rebels with a Cause !!
Jim Deane