I get mostly cards signed, at minor league games that is. With guys that I know have no problem signing multiple cards, I will ask them to sign howeve many I have. I don't ask guys to sign a lot if I know they won't either. Also, if I have many cards, I will ask a player if he could get a couple done, because I have them all ready for the entire series.
Yes, I have gotten 10-15 cards signed at once by players, but they had no problem with it, and a lot of the times, there aren't more than a few people around anyways.