We went to Phoenix for a diamondbacks game and when my husband bought his hat he got 20% discount. I dont know if its at all ball parks or not cant hurt to ask!!
San Diego Padres are very supportive of the military they can give 50% off or more for the games. They are also very family oriented park as you can take your own food in, the have the Friar shack for kids' food that is only $1 each, areas to sit in that start at $5 and go up from there.
We didnt even think to ask about tickets. And the only reason we got the discount on the hat was because we were paying and used our cc and she needed to see ID I usually ask all the time and he never asks. I'll ask next time we but tickets.