We got a small discount for universal park to park tickets ($5 each) on their already cheapest by far prices from Orlandoattractions.com (I researched quite extensively!). As we are UK military I telephoned their office as they do a discount via the rewards4forces site.
Because we are UK military we don't get the tax free tickets from Disney but FYI when these tickets aren't offered Orlandoattractions are cheaper than any of the other companies including shades of green and they have far more options of tickets (we got 7 day hoppers and hoppers wuth fun days). We saved a fair amount of money overall, got brilliant customer service and real tickets with free shipping in 7 days.
It's worth phoning the US office to see if they do discounts too.