It's getting easier and easier to be HFCS free in the US. I try to avoid it by choice and have noticed several brands that have quietly switched back to sugar even just in the last 2-3 months. Not only do many people avoid it either for medical reasons or choice, but it's gotten more expensive to use. Several of the brands I've noticed switch (especially of candy) are the cheap brands, while the more expensive brands continue to use HFCS.
Is all Heinz ketchup HFCS-free? That's one brand I haven't checked recently, but last I'd heard only part of their line was HFCS-free (they do print ingredients on the packets you get at QS-type restaurants so easy to check in those places). Hunt's ketchup used to be HFCS-free, but I've seen things stating that it now uses HFCS again. Hellmann's mayonnaise (it's the same as Best Food brand mayonnaise) only uses sugar. Mustards are usually HFCS-free. The two condiments I'd expect to be hardest to find without HFCS are BBQ sauce and sweet pickle relish. They're the ones I have trouble finding HFCS-free in grocery stores.
For people who like sodas (but don't/can't do diet sodas), Sierra Mist is HFCS free. Many small local brands (less likely to be found at WDW) are HFCS free. If any of the EPCOT WS places import their sodas, most imported sodas use sugar (I know that's true with imported Cokes).
You will still need to read ingredients, but there are definitely many foods/brands that don't use HFCS. The one very common food which could "hide" HFCS that I didn't mention earlier is bread and rolls. Several brands of bread are among the most recent switches to sugar I've noticed, but there are so many brands that I can't even estimate the chance of it being in the ones WDW orders.
Related: Does anyone know if in American ingredient lists using term "corn syrup" can mean high fructose corn syrup? I've always assumed corn syrup was a more general term that companies could use to try to mask using HFCS, but there definitely are other types of corn syrup. I'm just curious and wasn't sure if anyone here knows.