No discount codes that I know of, but check your local radio stations (especially AC stations, or any other stations geared to women. . . Disney likes to deal with stations that have moms listening)
I work for Clear Channel and we get a TON of coupons for free tickets every year when Disney on Ice comes - in fact, the same show the week before your dates, LOL. Unfortunately I'll miss it this year - fortunately for me though, I'll be missing it to go to Italy, ha! If I have to pass up Disney, it better be for something good like Italy! Kinda stinks - the show starts the day after we leave! What a tease!
But yeah, we always have a TON of these coupons to give away (instead of actual hard tickets, Disney send us the coupons so the listeners can choose their own seats or buy more seats all together. . . makes it easier on families to have that flexibility) We give them away on air, we give them away at remotes. . . I'd say call local stations and ask if they have or will be getting these, and how they will be giving them away. I was running a remote this morning and my PD was giving some away to just whoever showed up at the car dealership and asked for them. So definitely check your local radio stations out.
To narrow it down, check advertising. . . usually ads in the paper will have a "sponsored by" on there letting you know which stations or companies are spponsoring. . . THESE are the people that will have the free tickets. If you can't find an ad, call the venue and ask someone there who locally is sponsoring the event.
Check for Meet and Greets too - my station does a M&G every year for a handfull of winners. I've taken my little cousin each year to meet Mickey and Minnie - one of the perks of working there, ha! Last year we were right in front and she ended up with the drawing that Jane does of Tarzan. . . Jane's father (blanked on his name) ripped it off and skated it over to her.