Half at best maybe!
I used to do it all the time, I used to write to LA Angels baseball team, and i got about 100 signed over the years. Mostly I am sending 4 or 5 cards to the players that I liked back in the day, the kids are helping so its fun for all of us.
Some of the addresses I have sent to are wrong, some probably just get chucked in the bin, but any back is cool. We only started last week, trying to send 5 a week.