Oh, I know where you're talking about. Do they pay for parking or do you have to pay yourself?
If you have to park yourself, there's a garage called Down Under on Lombard street. It's super easy to get into and out of. It's also about a block away from the convention center. Staffed (though the staff will nag you to pay before you leave...*sigh*). Should be about $20 for the day.
You're actually a bit of a way from the stadium. Camden Yards and M&T Bank Stadium are right next to each other, and the convention center is on the Camden Yards side. I don't think you'll have it too bad leaving. People tend to leave the game in intervals, especially when it's cold out. Plus, you won't be near the main stadium parking lot.
Just watch out for idiots driving around the city (they like to do stupid stuff like change lanes in the middle of an intersection...) and if you have a chance, go check out the Inner Harbor.