I've hit 2 soft openings in the past couple of years - 1 knowing about it, the other not knowing about it.
Mission Space was due to open in the fall, yet when we were there in July/August, you could walk up and get a fast pass, or if early in the morning, just walk on (about a 5 minute wait).
This past year, I happened to be on a 1 day trip, and drove to Epcot, and asked at the ticket window is Soarin was open (soft opening). She said that she could not promise that the ride would be open, but they planned on taking riders that day. What this means, is that if they find a glitch, or if a glitch stops the attraction, you might not get to ride it that day.
So, after all of this, what does it mean?
We are going to be there late Feb/early March, and I would anticipate being able to ride on the attraction. As for your case, walk by the attraction, and see if they are taking riders that day!