Being Hispanic is no longer unique, especially in Texas.
I have a daughter who is Chinese, but you’d never know that by reading her transcripts, resume, or interests. There just isn’t a clue in her name, her activities, her course of study. If she wanted people to know, she could put hints on there or even outright say it. Sometimes when she first meets people you can see the surprise on their faces when they match the background info to the person standing in front of them. It has never mattered, or if it has, she moves on from that situation because she, like you, doesn’t want it to matter. When she applied to college a mistake was made and there were two applications, one where she checked the race box and one where she didn’t, and she was accepted off both applications (yes, we received two letters, slightly different names).
As suggested above, don’t check the race box, don’t list activities that identify you as Hispanic. I don’t think they care as much as you think they do. They want to know that you have done the prep work in undergrad, that you have thought about their program and how you can benefit from it, and how you can contribute to the department. At the PhD level, it is not about a trophy for every player for participation. Sure they want diversity because it helps them, but not at the expense of strong candidates.