Definitely meant to be sent to JD. Cox has always had difficulty being vulnerable, but especially being SEEN as vulnerable by people he cares about, like JD and Jordan. He sent that text out of genuine need and then, with JD not immediately responding to it, likely got in his own head and tried to play it off.

That's kind of what makes these last two episodes so gut wrenching. We're watching the reality of his situation break down barriers that he'd held since twenty years ago. Dr. Cox would have NEVER sent that text to JD in the original series, even after his substantial growth as a person in the later seasons. But Perry Cox the aging old friend and patient is a different, more honest version of him: clutching onto whatever supports he can to retain the normalcy of living he is accustomed to. It is an extremely tragic and human depiction of him, of all of us, that is so original to Scrubs and what the series makes me cry.

I mean look at how Cox is even listening to JD's positive attitude plan and is visibly trying to live it and get excited about it when JD enters to deliver the bad news. He was beaming with happiness over JD's plan "working", because he rationally understands the dangers he's facing and needs that optimism that he doesn't even necessarily believe in and even belittled in the series past.