Those tournaments typically take the highest of your Regular and Blitz ratings for pairings and prizes, and since you are unrated in Blitz, your Regular rating is used for everything. Therefore, you should be eligible for the U1600 prize.
USCF Blitz Rating Prizes for Players Unrated in Blitz

Those tournaments typically take the highest of your Regular and Blitz ratings for pairings and prizes, and since you are unrated in Blitz, your Regular rating is used for everything. Therefore, you should be eligible for the U1600 prize.
Something vaguely like this was said (i.e., "for pairings and prizes") on the poster, so I think you are right. Thanks.
I am thinking about playing the Chicago Open's Sunday night blitz tournament. I have a regular and quick rating under 1600, but I am unrated in blitz. The poster for the tournament () gives prizes for 2200/Unr and 2000/Unr, but I am assuming that these are for cases in which players are completely unrated (i.e., no regular/classic, quick rating, and blitz rating). Would I be eligible for the U1600 blitz prize?
Maybe there are some USCF tournament directors (or players) on here who would know?