Dowbaseballclub,
Keep that card, and any others you receive, in a file folder. It's mostly a nice souvenir of a very exciting time in your life. Don't contact the scout unless he says something like, "call me if you have any questions."
There were some who did say that, after some in home visits. Mostly they were trying to figure out how signable our son was, and wanted him to let them know if he had any change in what he was asking or plans (going to school vs. signing) leading up to the draft.
We never called any scout to ask anything like, "So what do you think?" or "What are my chances?" But we did call a couple just before the draft if they had left those instructions with us.
Sitting tight and not calling at this time of year is hard, but I think with MLB that is pretty much what you need to do.